commit f9cd6248ec8970fbff3ead9cad60fed53102ae0a
Author: Nanokloon <mathzone1@outlook.com>
Date:   Sat Jun 14 23:26:42 2025 +0200

    all

diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..cc864a9
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,56 @@
+cmake_minimum_required(VERSION 3.30)
+project(c C)
+
+set(CMAKE_C_STANDARD 17)
+set(INCLUDE_DIRECTORIES ./)
+include_directories()
+
+add_executable(stack_test stack/stack.c stack/stack.h stack/stack_test.c
+        cell/cell.c
+        cell/cell.h)
+
+add_executable(maze-nolib
+        leelib/leelib.c
+        leelib/leelib.h
+        stack/stack.c
+        stack/stack.h
+        lee-algorithm/lee-algorithm.c
+        lee-algorithm/lee-algorithm.h
+        cell/cell.c
+        cell/cell.h
+        robot/robot.c
+        robot/robot.h
+        robot/simple-simulator.c
+        main.c
+        robot/simulator-moves.c
+        robot/challenges/challenge2.c
+        robot/challenges/challenge3.c
+        robot/challenges/challenges.h
+        robot/challenges/challenge4.c)
+
+add_executable(maze-libsp
+        leelib/leelib.c
+        leelib/leelib.h
+        stack/stack.c
+        stack/stack.h
+        lee-algorithm/lee-algorithm.c
+        lee-algorithm/lee-algorithm.h
+        cell/cell.c
+        cell/cell.h
+        robot/robot.c
+        robot/robot.h
+        communication/communication.c
+        communication/communication.h
+        communication/utils.c
+        communication/utils.h
+        main.c
+        robot/controller-moves.c
+        robot/remote.c
+        robot/challenges/challenges.h
+        robot/challenges/challenge2.c
+        robot/challenges/challenge3.c
+        robot/challenges/challenge4.c)
+
+target_link_libraries(maze-libsp serialport m)
+target_link_libraries(maze-nolib m)
+target_link_libraries(stack_test m)
diff --git a/Testing/Temporary/LastTest.log b/Testing/Temporary/LastTest.log
new file mode 100644
index 0000000..20a4f99
--- /dev/null
+++ b/Testing/Temporary/LastTest.log
@@ -0,0 +1,3 @@
+Start testing: Jun 05 17:03 CEST
+----------------------------------------------------------
+End testing: Jun 05 17:03 CEST
diff --git a/cell/cell.c b/cell/cell.c
new file mode 100644
index 0000000..1a8995b
--- /dev/null
+++ b/cell/cell.c
@@ -0,0 +1,15 @@
+//
+// Created by nano on 5/1/25.
+//
+
+#include "cell.h"
+
+int cell_equals(cell a, cell b) {
+	return (a.x == b.x && a.y == b.y);
+}
+
+void cell_add(cell *c, cell a, cell b) {
+	c->x = a.x + b.x;
+	c->y = a.y + b.y;
+}
+
diff --git a/cell/cell.h b/cell/cell.h
new file mode 100644
index 0000000..c5cd34c
--- /dev/null
+++ b/cell/cell.h
@@ -0,0 +1,19 @@
+//
+// Created by nano on 5/1/25.
+//
+
+#ifndef CELL_H
+#define CELL_H
+
+
+typedef struct cell {
+	int x;
+	int y;
+} cell;
+
+int cell_equals(cell a,cell b);
+void cell_add(cell *c, cell a, cell b);
+
+
+
+#endif //CELL_H
diff --git a/communication/communication.c b/communication/communication.c
new file mode 100644
index 0000000..72bdf77
--- /dev/null
+++ b/communication/communication.c
@@ -0,0 +1,210 @@
+//
+// Created by nano on 4/26/25.
+//
+
+#include "communication.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+
+
+struct sp_port *port;
+struct sp_event_set *event_data_ready;
+struct sp_event_set *event_ready_for_tx;
+
+/**
+ * Initializes the serial communication for the usb -> uart board
+ */
+void comm_init_communication() {
+	struct sp_port **port_list;
+	comm_get_port_list(&port_list);
+	int portnr = 0;
+	comm_list_serial_ports(port_list);
+	printf("Chose a port: ");
+	scanf("%d", &portnr);
+	sp_copy_port(port_list[portnr], &port);
+	sp_free_port_list(port_list);
+	comm_open_port();
+}
+
+void comm_get_port_list(struct sp_port ***port_list) {
+	enum sp_return result = sp_list_ports(port_list);
+	if (result != SP_OK) {
+		printf("Error listing serial ports\n");
+		exit(-1);
+	}
+}
+
+void comm_list_serial_ports(struct sp_port **port_list) {
+	printf("Port list:\n");
+	for (int i = 0; port_list[i] != NULL; i++) {
+		char *port_name = sp_get_port_name(port_list[i]);
+		printf("Port %d: %s\n", i, port_name);
+	}
+}
+/**
+	 * Opens communication to the selected serial port and sets the correct parameters for the zigbee carrier board.
+	 * Also add event to see when data arrives.
+	 */
+void comm_open_port() {
+
+	check(sp_open(port, SP_MODE_READ_WRITE));
+	check(sp_set_baudrate(port, 9600));
+	check(sp_set_bits(port, 8));
+	check(sp_set_parity(port, SP_PARITY_NONE));
+	check(sp_set_stopbits(port, 1));
+
+	check(sp_new_event_set(&event_data_ready));
+	check(sp_new_event_set(&event_ready_for_tx));
+
+	sp_add_port_events(event_data_ready, port, SP_EVENT_RX_READY);
+	sp_add_port_events(event_ready_for_tx, port, SP_EVENT_TX_READY);
+}
+
+/**
+	 * Ends the serial communication for the usb -> uart board
+	 */
+void comm_end_communication() {
+	check(sp_close(port));
+	sp_free_port(port);
+}
+
+/**
+ * Wait till there is data available.
+ * @param timeout how much time in ms to wait for the data
+ * @returns SP_OK if data is ready.
+ * @returns SP_ERR_FAIL if data was not available before timeout ended.
+ */
+int comm_await_data_ready(int timeout) {
+	// Await data from the robot
+	return sp_wait(event_data_ready, timeout);
+}
+
+/**
+ * Wait till you can transmit again .
+ * @param timeout how much time in ms to wait for the data
+ * @returns SP_OK if data is ready.
+ * @returns SP_ERR_FAIL if uart module wasnt ready for transmit before timeout ended.
+ */
+int comm_await_ready_for_tx(int timeout) {
+	return sp_wait(event_ready_for_tx, timeout);
+}
+
+
+/**
+ * Read a number of bytes from the buffer, store them in data without blocking the process.
+ * @param data array where to store the data
+ * @param amount_of_bytes
+ * @return ALL_BYTES if the number of expected bytes was read
+ * @return NOT_ENOUGH_BYTES if read less than expected
+ * @return ERROR if read fails
+ */
+comm_result comm_nonblocking_read(byte *data, int amount_of_bytes) {
+	//read available data
+	int recv_bytes = sp_nonblocking_read(port, data, amount_of_bytes);
+	if (recv_bytes == amount_of_bytes) {
+		return ALL_BYTES;
+	}
+	if (recv_bytes >= 0) {
+		return NOT_ENOUGH_BYTES;
+	}
+	return ERROR;
+}
+
+/**
+ * Read a number of bytes from the buffer, store them in data, with a number of ms to wait in case that amount of data is not available..
+ * @param data array where to store the data
+ * @param amount_of_bytes
+ * @param timeout how much time in ms to wait for all data to be available.
+ * @return ALL_BYTES if the number of expected bytes was read
+ * @return NOT_ENOUGH_BYTES if read less than expected
+ * @return ERROR if read fails
+ */
+comm_result comm_blocking_read(byte *data, int amount_of_bytes, int timeout) {
+	//read available data
+	int recv_bytes = sp_blocking_read(port, data, amount_of_bytes, timeout);
+	printf("RECV: %d\n",*data);
+	if (recv_bytes == amount_of_bytes) {
+		return ALL_BYTES;
+	}
+	if (recv_bytes >= 0) {
+		return NOT_ENOUGH_BYTES;
+	}
+	return ERROR;
+}
+
+/**
+ * Write a number of bytes to the buffer, from data, with a number of ms to wait in case that amount of data is not available..
+ * @param data array where to store the data
+ * @param amount_of_bytes
+ * @param timeout how much time in ms to wait for all data to be available.
+ * @return ALL_BYTES if the number of expected bytes was read
+ * @return NOT_ENOUGH_BYTES if read less than expected
+ * @return ERROR if read fails
+ */
+comm_result comm_blocking_write(byte *data, int amount_of_bytes, int timeout) {
+	// we are writing 8 bit bytes to the fpga anyways and pc -> fpga only needs to tell what do to next, can be fit in 8 bits
+	int sent_bytes = sp_blocking_write(port, data, amount_of_bytes, timeout);
+	printf("SEND: %d \n",*data);
+
+	if (sent_bytes == amount_of_bytes) {
+		return ALL_BYTES;
+	}
+	if (sent_bytes >= 0) {
+		return NOT_ENOUGH_BYTES;
+	}
+	return ERROR;
+}
+
+/**
+ * Write a number of bytes to the buffer, from data.
+ * @param data array where to store the data
+ * @param amount_of_bytes
+ * @return ALL_BYTES if the number of expected bytes was read
+ * @return NOT_ENOUGH_BYTES if read less than expected
+ * @return ERROR if read fails
+ */
+comm_result comm_nonblocking_write(byte *data, int amount_of_bytes) {
+	// we are writing 8 bit bytes to the fpga anyways and pc -> fpga only needs to tell what do to next, can be fit in 8 bits
+	int sent_bytes = sp_nonblocking_write(port, data, amount_of_bytes);
+	if (sent_bytes == amount_of_bytes) {
+		return ALL_BYTES;
+	}
+	if (sent_bytes >= 0) {
+		return NOT_ENOUGH_BYTES;
+	}
+	return ERROR;
+}
+
+//Check if bytes are left to be sent
+int comm_output_waiting() {
+	return sp_output_waiting(port);
+}
+
+/** Helper function for error handling. Taken from libserialport examples */
+int check(enum sp_return result) {
+	/* For this example we'll just exit on any error by calling abort(). */
+	char *error_message;
+	switch (result) {
+		case SP_ERR_ARG:
+			printf("Error: Invalid argument.\n");
+			abort();
+		case SP_ERR_FAIL:
+			error_message = sp_last_error_message();
+			printf("Error: Failed: %s\n", error_message);
+			sp_free_error_message(error_message);
+			abort();
+		case SP_ERR_SUPP:
+			printf("Error: Not supported.\n");
+			abort();
+		case SP_ERR_MEM:
+			printf("Error: Couldn't allocate memory.\n");
+			abort();
+		case SP_OK:
+		default:
+			return result;
+	}
+}
diff --git a/communication/communication.h b/communication/communication.h
new file mode 100644
index 0000000..0cb7d56
--- /dev/null
+++ b/communication/communication.h
@@ -0,0 +1,89 @@
+//
+// Created by nano on 4/26/25.
+//
+#ifndef COMMS_H
+#define COMMS_H
+#include <libserialport.h>
+#include <sys/types.h>
+
+typedef u_int8_t byte;
+
+typedef enum { ALL_BYTES, NOT_ENOUGH_BYTES, ERROR } comm_result;
+int comm_output_waiting() ;
+/**
+ *  Initializes the serial communication for the usb -> uart board
+ */
+void comm_init_communication();
+
+/**
+ * Generates port list from present serial ports.
+ * @param port_list pointer to port list to set.
+ */
+void comm_get_port_list(struct sp_port ***port_list);
+
+void comm_list_serial_ports(struct sp_port **port_list);
+
+/**
+ * Opens communication to the selected serial port and sets the correct parameters for the zigbee carrier board.
+ */
+void comm_open_port();
+
+/**
+ * Ends the serial communication for the usb -> uart board
+ */
+void comm_end_communication();
+
+/**
+ * Await fresh data from the serial port
+ * @param timeout timeout for waiting for a byte to be ready to read
+ * @return if there is data available (1 or 0)
+ */
+int comm_await_data_ready(int timeout);
+
+/**
+ * Check if the serial port is ready to be written to.
+ * @param timeout timeout for waiting for a byte to be ready to read
+ * @return if data can be written (1 or 0)
+ */
+int comm_await_ready_for_tx(int timeout);
+
+/**
+ *Do a nonblocking read from the serial port
+ *@param data pointer to data to read
+ *@param amount_of_bytes amount of bytes to read from uart buffer
+ *@return if whole buffer was filled, part of the buffer was filled or error
+ */
+comm_result comm_nonblocking_read(byte *data, int amount_of_bytes);
+
+/**
+ *Do a blocking read from the serial port
+ *@param data pointer to data to read
+ *@param amount_of_bytes amount of bytes to read from uart buffer
+ *@param timeout how long to wait for data to be filled
+ *@return if whole buffer was filled, part of the buffer was filled or error
+ */
+comm_result comm_blocking_read(byte *data, int amount_of_bytes, int timeout);
+
+/**
+ *Do a nonblocking write from the serial port
+ *@param data pointer to data to write
+ *@param amount_of_bytes amount of bytes to write to uart
+ *@return if whole buffer was written, part of the buffer was written or error
+ */
+comm_result comm_nonblocking_write(byte *data, int amount_of_bytes);
+
+/**
+ *Do a nonblocking write from the serial port
+ *@param data pointer to data to write
+ *@param amount_of_bytes amount of bytes to write to uart
+ *@param timeout how long to wait for data to be filled
+ *@return if whole buffer was written, part of the buffer was written or error
+ */
+comm_result comm_blocking_write(byte *data, int amount_of_bytes, int timeout);
+
+/** Helper function for error handling.
+ * Taken from libserialport examples. */
+int check(enum sp_return result);
+
+
+#endif //COMMS_H
diff --git a/communication/utils.c b/communication/utils.c
new file mode 100644
index 0000000..6844024
--- /dev/null
+++ b/communication/utils.c
@@ -0,0 +1,122 @@
+//
+// Created by nano on 4/26/25.
+//
+
+#include <stdlib.h>
+
+#include "utils.h"
+
+#include <stdio.h>
+
+#include "communication.h"
+
+#define ACK 16
+#define NOTHING_RECV 0
+
+/**Helper functions to convert from bits to bytes*/
+void byte_to_bit_array(byte bit_array[], byte data) {
+	for (int i = 0; i < 8; i++) {
+		bit_array[i] = (data >> i) & 1; //shift through all bits and check if they're 1
+	}
+}
+
+/**2's complement notation*/
+void bit_array_to_byte(const byte bit_array[], byte *data) {
+	*data = 0;
+	byte currentpow = 1;
+	for (int i = 0; i < 8; i++) {
+		*data += bit_array[i] * currentpow;
+		currentpow *= 2;
+	}
+}
+
+void comm_write_until_successful(byte d, int timeout) {
+	//while (comm_await_comm_awaready_for_tx(50)!=SP_OK) {} //wait indefinitely till you can send data
+	REWRITE:
+	comm_blocking_write(&d,1,timeout);
+
+	byte data;
+	int counter =0;
+	REREAD:
+	while (comm_blocking_read(&data,1,timeout) != ALL_BYTES) {counter ++; if (counter == 10) goto REWRITE;} //idk if this does anything but the code works so im not touching it
+
+	//data ? printf("RECV: %d \n",data) : 0;
+	counter++;
+	printf("Times Read %d",counter);
+	if (data == ACK) {
+		printf("ACK\n");
+	}
+	else if (counter !=10)
+		goto REREAD;
+	else
+		goto REWRITE;
+}
+
+#define CROSSING 0x20
+
+/**
+ * await data from the robot
+ * @param data data gotten from robot
+ * @return 1 if correct, -1 if retry required
+ */
+int comm_await_crossing(int timeout){
+	byte data;
+	int run =1;
+	printf("AWAITING CROSSING\n");
+	while (run){
+		comm_blocking_read(&data, 1,timeout);
+		printf("Read while expecting crossing: %d\n",data);
+		if (data==CROSSING) {
+			//printf("CROSSING\n");
+			run=0;
+			return 1;
+			break;
+		}
+	}
+	return -1;
+}
+
+#define SENSOR_NOTHING_AHEAD 5
+#define SENSOR_1_CROSSING_AHEAD 1
+#define SENSOR_2_CROSSING_AHEAD 2
+#define SENSOR_3_CROSSING_AHEAD 3
+#define SENSOR_4_CROSSING_AHEAD 4
+
+int comm_get_distance_sensor(int *len, int timeout) {
+	byte *data = malloc(sizeof(byte));
+	while (comm_blocking_read(data,1,timeout) == ALL_BYTES) {
+		printf("Got while expecting distance sensor: %d \n", *data);
+		switch (*data) {
+			case SENSOR_NOTHING_AHEAD:
+				*len=0;
+				free(data);
+				return 1;
+				break;
+			case SENSOR_1_CROSSING_AHEAD:
+				*len=1;
+				free(data);
+				return 1;
+				break;
+			case SENSOR_2_CROSSING_AHEAD:
+				*len=3;
+				free(data);
+				return 1;
+				break;
+			case SENSOR_3_CROSSING_AHEAD:
+				*len=5;
+				free(data);
+				return 1;
+				break;
+			case SENSOR_4_CROSSING_AHEAD:
+				*len=7;
+				free(data);
+				return 1;
+				break;
+			default:
+				printf("wat\n");
+				break;
+		}
+	}
+	free(data);
+	return 0;
+}
\ No newline at end of file
diff --git a/communication/utils.h b/communication/utils.h
new file mode 100644
index 0000000..4dbeea9
--- /dev/null
+++ b/communication/utils.h
@@ -0,0 +1,20 @@
+//
+// Created by nano on 4/26/25.
+//
+#include <sys/types.h>
+
+
+#ifndef COMM_UTILS_H
+#define COMM_UTILS_H
+typedef u_int8_t byte;
+
+void byte_to_bit_array(byte *bit_array, byte data);
+
+void bit_array_to_byte(const byte bit_array[], byte *data);
+
+void comm_write_until_successful(byte d, int timeout);
+
+int comm_await_crossing(int timeout);
+
+int comm_get_distance_sensor(int *len, int timeout) ;
+#endif //COMM_UTILS_H
diff --git a/lee-algorithm/lee-algorithm.c b/lee-algorithm/lee-algorithm.c
new file mode 100644
index 0000000..87e5672
--- /dev/null
+++ b/lee-algorithm/lee-algorithm.c
@@ -0,0 +1,148 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "lee-algorithm.h"
+
+#include "../stack/stack.h"
+#include "../cell/cell.h"
+#include "../communication/utils.h"
+#include "../robot/robot.h"
+
+
+// Maze en standaard Lee-functies
+
+int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE] = {
+	{ -1, -1, -1, 0, -1, 0, -1, 0, -1, -1, -1},
+	{ -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1},
+	{ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1},
+	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+	{ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1},
+	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+	{ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1},
+	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+	{ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1},
+	{ -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1},
+	{ -1, -1, -1, 0, -1, 0, -1, 0, -1, -1, -1,}
+};
+
+const cell neighbours[4] = {{-1, 0}, {0, 1}, {1,}, {0, -1}}; // NORTH EAST SOUTH WEST
+const cell crossing_neighbours[4] = {{-2, 0}, {0, 2}, {2,0}, {0, -2}};
+
+void lee_run(robot r, cell targetCell, stack *moves) {
+	int assignmentMatrix[MAZE_SIZE][MAZE_SIZE];
+	memcpy(assignmentMatrix, unexpanded_matrix, sizeof(assignmentMatrix));
+	lee_expand(assignmentMatrix, r.pos, targetCell);
+	lee_trace(assignmentMatrix, r, targetCell, moves);
+	stack_invert(moves);
+}
+
+void lee_expand(int assignmentMatrix[MAZE_SIZE][MAZE_SIZE], cell startCell, cell targetCell) {
+	int v = 1;
+	assignmentMatrix[targetCell.x][targetCell.y] = v;
+	while (assignmentMatrix[startCell.x][startCell.y] == 0) {
+		for (int i = 0; i < MAZE_SIZE; i++) {
+			for (int j = 0; j < MAZE_SIZE; j++) {
+				if (assignmentMatrix[i][j] == v) {
+					for (int k = 0; k < 4; k++) {
+						cell neighbour;
+						cell_add(&neighbour, (cell){i, j}, neighbours[k]);
+						if (isInBound(neighbour) && assignmentMatrix[neighbour.x][neighbour.y] == 0) {
+							assignmentMatrix[neighbour.x][neighbour.y] = v + 1;
+						}
+					}
+				}
+			}
+		}
+		v += 1;
+	}
+}
+
+void lee_trace(int assignmentMatrix[MAZE_SIZE][MAZE_SIZE], robot r, cell targetCell, stack *stack) {
+	robot tempBot = r;
+	printf("\n");
+	while (!cell_equals(tempBot.pos, targetCell)) {
+		// check forward first,as its most efficient move
+		cell neighbourCell;
+		cell_add(&neighbourCell, tempBot.pos, neighbours[tempBot.dir]);
+		if (isInBound(neighbourCell) &&
+			assignmentMatrix[neighbourCell.x][neighbourCell.y] > 0 &&
+			assignmentMatrix[neighbourCell.x][neighbourCell.y] < assignmentMatrix[tempBot.pos.x][tempBot.pos.y]) {
+			tempBot.pos = neighbourCell;
+			//if (isValidCrossing(tempBot.pos) ) {
+				stack_push(stack, neighbours[tempBot.dir]);
+			//}
+			continue;
+		}
+		// check rest of directions
+		for (int i = 0; i < 4; i++) {
+			cell_add(&neighbourCell, tempBot.pos, neighbours[(tempBot.dir + i) % 4]);
+			//ugly calculation as to check all 3 other directions other than the main one
+			if (isInBound(neighbourCell) &&
+				assignmentMatrix[neighbourCell.x][neighbourCell.y] > 0 &&
+				assignmentMatrix[neighbourCell.x][neighbourCell.y] < assignmentMatrix[tempBot.pos.x][tempBot.pos.y]) {
+				tempBot.pos = neighbourCell;
+				spin(&r, tempBot.dir);
+				//if (isValidCrossing(tempBot.pos)) {
+					stack_push(stack, neighbours[(tempBot.dir + i) % 4]);
+				//}
+				break;
+			}
+		}
+	}
+}
+
+int validatePath(robot r, stack s) {
+	robot temp = r;
+	for (int i = 0; i < s.length; i++) {
+			cell_add(&temp.pos, temp.pos,s.data[i]);
+			if (unexpanded_matrix[temp.pos.x][temp.pos.y] < 0) {
+				return 0;
+		}
+	}
+	return 1;
+}
+
+extern int firstMove;
+void followPath(robot *r, stack *path,int visited[MAZE_SIZE][MAZE_SIZE]) {
+	while (path->length > 0) {
+		cell currentCell = stack_pop(path);
+		int result = move(r,currentCell);
+		comm_await_crossing(2000);
+		comm_discard_sensor_data(1000);
+		visited[r->pos.x][r->pos.y] = 5;
+		if (result == 0) {
+			move(r,currentCell);
+			comm_await_crossing(2000);
+			comm_discard_sensor_data(1000);
+			visited[r->pos.x][r->pos.y] = 5;
+		}
+		printMatrix_with_current_pos(visited,*r);
+	}
+}
+
+int isInBound(const cell c) {
+	if (c.x >= 0 && c.x < MAZE_SIZE &&
+		c.y >= 0 && c.y < MAZE_SIZE) {
+		return 1;
+		}
+	return 0;
+}
+
+
+int isStation(const cell c) {
+	if (c.x == 0 || c.x == MAZE_SIZE - 1 ||
+		c.y == 0 || c.y == MAZE_SIZE - 1){
+		return 1;
+		}
+	return 0;
+
+}
+int isValidCrossing(const cell c) {
+	if (c.x > 0 && c.x < MAZE_SIZE - 1 &&
+		c.y > 0 && c.y < MAZE_SIZE - 1 &&
+		c.x % 2 == 1 && c.y % 2 == 1 &&
+		unexpanded_matrix[c.x][c.y]==0) {
+		return 1;
+		}
+	return 0;
+}
diff --git a/lee-algorithm/lee-algorithm.h b/lee-algorithm/lee-algorithm.h
new file mode 100644
index 0000000..c54981b
--- /dev/null
+++ b/lee-algorithm/lee-algorithm.h
@@ -0,0 +1,25 @@
+//
+// Created by nano on 4/30/25.
+//
+
+#ifndef LEE_ALGORITHM_H
+#define LEE_ALGORITHM_H
+
+#include "../stack/stack.h"
+#include "../robot/robot.h"
+
+#define MAZE_SIZE 11
+
+void followPath(robot *r, stack *path,int visited[MAZE_SIZE][MAZE_SIZE]);
+
+void lee_run(robot r, cell targetCell, stack *moves);
+
+void lee_expand(int assignmentMatrix[MAZE_SIZE][MAZE_SIZE], cell startCell,cell targetCell) ;
+void lee_trace(int assignmentMatrix[MAZE_SIZE][MAZE_SIZE], robot r, cell targetCell, stack *stack);
+
+int validatePath(robot r, stack s);
+
+int isInBound(cell c);
+int isStation(cell c);
+int isValidCrossing(cell c);
+#endif //LEE_ALGORITHM_H
diff --git a/leelib/leelib.c b/leelib/leelib.c
new file mode 100644
index 0000000..1229a93
--- /dev/null
+++ b/leelib/leelib.c
@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "../lee-algorithm/lee-algorithm.h"
+
+void readEdge (int *i, int *j)
+/* Scans input to read a blocked edge.
+   Returns the indices i and j in m[13][13] of an edge.
+   Call this function with pointers to the variables 
+   that should receive the values, e.g.
+       readEdge (&x, &y);
+*/
+{
+   int cx, cy;
+   char d;
+   scanf ("%d %d %c", &cy, &cx, &d);
+   if (d == 's') { 
+      *i = 2 + cy * 2 + 1; 
+      *j = 2 + cx * 2; 
+   }
+   else if (d == 'e') { 
+      *i = 2 + cy * 2; 
+      *j = 2 + cx * 2 + 1; 
+   }
+   else { 
+      fprintf (stderr, "error on direction: %c\n", d); 
+      exit (1); 
+   }  
+}
+
+void readStation (int *i, int *j)
+/* Scans input to read a station.
+   Returns the indices i and j in m[13][13] of a station.
+ */
+{
+   int s;
+   scanf ("%d", &s);
+   switch (s) {
+      case 1: *i = 10, *j = 3; break;
+      case 2: *i = 10, *j = 5; break;
+      case 3: *i = 10, *j = 7; break;
+      case 4: *i = 7, *j = 10; break;
+      case 5: *i = 5, *j = 10; break;
+      case 6: *i = 3, *j = 10; break;
+      case 7: *i = 0, *j = 7; break;
+      case 8: *i = 0, *j = 5; break;
+      case 9: *i = 0, *j = 3; break;
+      case 10: *i = 3, *j = 0; break;
+      case 11: *i = 5, *j = 0; break;
+      case 12: *i = 7, *j = 0; break;
+      default: fprintf (stderr, "Illegal station\n"); exit (-1);
+   }
+}
+
+void printCrossingName (int i, int j)
+/* Print the name of the crossing with indices i and j in m[13][13]/ */
+{
+   if ((i-2)%2 == 0 && (j-2)%2 == 0)
+      printf ("c%d%d ",  (i-2)/2, (j-2)/2);
+}
+
+void printMatrix (int m[][MAZE_SIZE])
+/* Print the elements of the matrix m[13][13]. */
+{
+   int i, j;
+
+   for (i = 0; i < MAZE_SIZE; i++) {
+      for (j = 0; j < MAZE_SIZE; j++) {
+         printf ("%2d ", m[i][j]);
+      }
+      printf ("\n");
+   }
+}
diff --git a/leelib/leelib.h b/leelib/leelib.h
new file mode 100644
index 0000000..a7192f8
--- /dev/null
+++ b/leelib/leelib.h
@@ -0,0 +1,19 @@
+void readEdge (int *i, int *j);
+/* Scans input to read a blocked edge.
+   Returns the indices i and j in m[13][13] of an edge.
+   Call this function with pointers to the variables 
+   that should receive the values, e.g.
+       readEdge (&x, &y);
+*/
+
+void readStation (int *i, int *j);
+/* Scans input to read a station.
+   Returns the indices i and j in m[13][13] of a station.
+ */
+
+void printCrossingName (int i, int j);
+/* Print the name of the crossing with indices i and j in m[13][13]/ */
+
+void printMatrix (int m[][11]);
+/* Print the elements of the matrix m[13][13]. */
+
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..7b199db
--- /dev/null
+++ b/main.c
@@ -0,0 +1,46 @@
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "cell/cell.h"
+#include "communication/communication.h"
+#include "leelib/leelib.h"
+#include "robot/robot.h"
+#include "robot/challenges/challenges.h"
+
+extern int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE];
+extern int visited[MAZE_SIZE][MAZE_SIZE];
+
+extern const cell neighbours[4];
+
+
+void addBlock(robot r, cell move, direction dir, cell targetCell, stack *s);
+
+int main(int argc, char *argv[]) {
+	/* read the starting and end station.*/
+	if (argc < 2) {
+		printf("NOT ENOUGH ARGUMENTS \n");
+		printf("USAGE: ./maze <CHALLENGE NR or 0 for simple remote> \n");
+		return -1;
+	}
+	switch (strtol(argv[1],NULL, 10)) {
+			case 0:
+				simple_control();
+				break;
+			case 2:
+				challenge_2();
+				break;
+			case 3:
+				challenge_3((cell){10,3});
+				break;
+			case 4:
+				challenge_4((cell){10,3});
+				break;
+			default:
+				printf("DOESNT WORK YET \n");
+				break;
+		}
+
+	return 0;
+}
+
diff --git a/maze-editor.html b/maze-editor.html
new file mode 100644
index 0000000..6eba70b
--- /dev/null
+++ b/maze-editor.html
@@ -0,0 +1,127 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <title>Maze Editor</title>
+    <style>
+      body {
+        font-family: Arial, sans-serif;
+        margin: 20px;
+      }
+      h1 {
+        color: #444;
+      }
+      .maze-container {
+        display: flex;
+        justify-content: center;
+      }
+      table {
+        border-collapse: collapse;
+      }
+      td {
+        border: 1px solid #ccc;
+        width: 20px;
+        height: 20px;
+        text-align: center;
+      }
+      input[type="checkbox"] {
+        width: 20px;
+        height: 20px;
+        margin: 0;
+      }
+      .cell-0 {
+        background-color: #fff;
+      }
+      .cell-1 {
+        background-color: #ddd;
+      }
+      .button {
+        margin-top: 20px;
+      }
+      #output {
+        font-family: monospace;
+        margin-top: 20px;
+      }
+      input[disabled] {
+        cursor: not-allowed;
+      }
+    </style>
+  </head>
+  <body>
+    <h1>Maze Editor</h1>
+    <div id="maze-container" class="maze-container"></div>
+    <button class="button" onclick="printArray()">Show Array</button>
+    <div id="output"></div>
+
+    <script>
+      const MAZE_SIZE = 11;
+      // Original matrix with -1's
+      const originalMatrix = [
+        [ -1, -1, -1, 0, -1, 0, -1, 0, -1, -1, -1 ],
+        [ -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1 ],
+        [ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1 ],
+        [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
+        [ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1 ],
+        [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
+        [ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1 ],
+        [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
+        [ -1, 0, -1, 0, -1, 0, -1, 0, -1, 0, -1 ],
+        [ -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1 ],
+        [ -1, -1, -1, 0, -1, 0, -1, 0, -1, -1, -1 ]
+      ];
+
+      // Work copy for editing
+      let mazeData = JSON.parse(JSON.stringify(originalMatrix));
+
+      function initMaze() {
+        const container = document.getElementById("maze-container");
+        container.innerHTML = "";
+        const table = document.createElement("table");
+        for (let i = 0; i < MAZE_SIZE; i++) {
+          const tr = document.createElement("tr");
+          for (let j = 0; j < MAZE_SIZE; j++) {
+            const td = document.createElement("td");
+            const checkbox = document.createElement("input");
+            checkbox.type = "checkbox";
+            checkbox.checked = mazeData[i][j] === -1;
+            // Disable if original value is -1 OR not at even indices
+            checkbox.disabled =
+              originalMatrix[i][j] === -1 ||
+              !(i % 2 === 0 || j % 2 === 0) ||
+            checkbox.addEventListener("change", function () {
+              mazeData[i][j] = this.checked ? -1 : 0;
+              updateCellClass(td, this.checked);
+            });
+            td.appendChild(checkbox);
+            updateCellClass(td, mazeData[i][j] === -1);
+            tr.appendChild(td);
+          }
+          table.appendChild(tr);
+        }
+        container.appendChild(table);
+      }
+
+      function updateCellClass(td, isWall) {
+        td.className = isWall ? "cell-1" : "cell-0";
+      }
+
+      function printArray() {
+        let output = "int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE] = {\n";
+        for (let i = 0; i < MAZE_SIZE; i++) {
+          output += "\t{";
+          for (let j = 0; j < MAZE_SIZE; j++) {
+            output += mazeData[i][j];
+            if (j < MAZE_SIZE - 1) output += ", ";
+          }
+          output += "}";
+          if (i < MAZE_SIZE - 1) output += ",";
+          output += "\n";
+        }
+        output += "};";
+        document.getElementById("output").textContent = output;
+      }
+
+      window.onload = initMaze;
+    </script>
+  </body>
+</html>
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..e69de29
diff --git a/robot/challenges/challenge2.c b/robot/challenges/challenge2.c
new file mode 100644
index 0000000..a65b16d
--- /dev/null
+++ b/robot/challenges/challenge2.c
@@ -0,0 +1,101 @@
+#include <stdio.h>
+#include <limits.h>
+#include <string.h>
+
+#include "../../communication/communication.h"
+#include "../../leelib/leelib.h"
+#include "../../lee-algorithm/lee-algorithm.h"
+#include "../challenges/challenges.h"
+
+extern int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE];
+extern const cell neighbours[4]; // SOUTH, EAST, WEST, NORTH
+
+
+int compute_path_length(cell from, cell to);
+
+
+
+void challenge_2() {
+	comm_init_communication();
+
+	cell start;
+	printf("Starting station: ");
+	readStation(&start.x, &start.y);
+	printf("\n");
+
+    robot r;
+	r.pos = start;
+	r.dir = getStartDirection(start);
+	//cell_add(&r.pos,r.pos,neighbours[r.dir]);
+    cell stations[3];
+	for(int i=0;i<3;i++){
+		printf("Station to visit %d: ",i+1);
+		readStation(&(stations[i].x),&(stations[i].y));
+		printf("\n");
+	}
+	int bestOrder[3];
+	int minTotal = INT_MAX;
+
+	// test alle 6 
+	for (int a = 0; a < 3; a++) {
+		for (int b = 0; b < 3; b++) {
+			if (b == a) continue;
+			for (int c = 0; c < 3; c++) {
+				if (c == a || c == b) continue;
+				int total = 0;
+				total += compute_path_length(start, stations[a]);
+				total += compute_path_length(stations[a], stations[b]);
+				total += compute_path_length(stations[b], stations[c]);
+				if (total < minTotal) {
+					minTotal = total;
+					bestOrder[0] = a;
+					bestOrder[1] = b;
+					bestOrder[2] = c;
+				}
+			}
+		}
+	}
+	int visited[MAZE_SIZE][MAZE_SIZE]={0};
+	memcpy(visited, unexpanded_matrix, sizeof(unexpanded_matrix));
+
+	// volg beste volgorde
+	for (int i = 0; i < 3; i++) {
+		cell target = stations[bestOrder[i]];
+		printf("\n[Station %d] Naar (%d, %d):\n", i+1, target.x, target.y);
+		stack path;
+		stack_init(&path);
+		lee_run(r, target, &path);
+		followPath(&r, &path,visited);
+		visited[r.pos.x][r.pos.y] = 5;
+		stack_free(&path);
+	}
+	printMatrix_with_current_pos(visited,r);
+	printAllMoves();
+	comm_end_communication();
+}
+
+int compute_path_length(const cell from, const cell to) { //modified expand phase to get maximum length
+	if (to.x == 999 && to.y == 999) return 999;
+	int tempMatrix[MAZE_SIZE][MAZE_SIZE];
+	memcpy(tempMatrix, unexpanded_matrix, sizeof(tempMatrix));
+	int steps = 1;
+	tempMatrix[to.x][to.y] = steps;
+	while (tempMatrix[from.x][from.y] == 0) {
+		for (int i = 0; i < MAZE_SIZE; i++) {
+			for (int j = 0; j < MAZE_SIZE; j++) {
+				if (tempMatrix[i][j] == steps) {
+					for (int k = 0; k < 4; k++) {
+						cell n;
+						cell_add(&n,(cell){i,j}, neighbours[k]);
+						if (isInBound(n) && tempMatrix[n.x][n.y] == 0) {
+							tempMatrix[n.x][n.y] = steps + 1;
+						}
+					}
+				}
+			}
+		}
+		steps++;
+		if (steps > 1000) break; 
+	}
+	return tempMatrix[from.x][from.y] ? tempMatrix[from.x][from.y] : INT_MAX;
+}
diff --git a/robot/challenges/challenge3.c b/robot/challenges/challenge3.c
new file mode 100644
index 0000000..3945be1
--- /dev/null
+++ b/robot/challenges/challenge3.c
@@ -0,0 +1,169 @@
+#include <stdio.h>
+#include "../../cell/cell.h"
+#include <limits.h>
+#include <string.h>
+
+#include "../robot.h"
+#include "../../communication/communication.h"
+#include "../../communication/utils.h"
+#include "../../lee-algorithm/lee-algorithm.h"
+#include "../../leelib/leelib.h"
+#include "../challenges/challenges.h"
+
+#define MAZE_SIZE 11
+
+extern int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE];
+extern const cell neighbours[4]; // volgorde: SOUTH, EAST, WEST, NORTH
+
+
+int compute_path_length(cell from, cell to);
+void find_best_order_of_3(cell start,cell stations[3],int bestOrder[3]);
+void find_best_order_of_2(cell start,cell stations[2],int bestOrder[2]);
+
+
+void challenge_3(cell start) {
+	comm_init_communication();
+	int visited[MAZE_SIZE][MAZE_SIZE]={0};
+	memcpy(visited, unexpanded_matrix, sizeof(unexpanded_matrix));
+
+	robot r;
+	r.pos = start;
+	r.dir = getStartDirection(start);
+
+	stack path;
+	stack_init(&path);
+
+	int visitedStations=0,run=1,bestOrder[3];
+
+	cell all_stations[3];
+	cell last_stations[2];
+
+	for(int i=0;i<3;i++){
+		printf("Station to visit %d: ",i+1);
+		readStation(&(all_stations[i].x),&(all_stations[i].y));
+		printf("\n");
+	}
+
+	find_best_order_of_3(start,all_stations,bestOrder);
+
+	cell target = all_stations[bestOrder[0]];
+	lee_run(r, target, &path);
+
+	while (run){
+		printf("\n[Station %d] Naar (%d, %d):\n", visitedStations +1 ,target.x, target.y);
+		switch (visitedStations) {
+			case 0:
+				if (!followPath_with_blockages(&r, &path,visited)) {
+					find_best_order_of_3(r.pos,all_stations,bestOrder);
+					target = all_stations[bestOrder[0]];
+					stack_reinit(&path);
+					lee_run(r, target, &path);
+				}
+				else {
+					//robot is in the station, manually spin
+					unexpanded_matrix[r.pos.x][r.pos.y]=0; //bugfix, somehow something was causing for a blockage to show up at station.
+					turnRight(&r);
+					r.dir=(r.dir+1)%4;
+					comm_await_crossing(2000);
+					comm_discard_sensor_data(1000);
+					visitedStations++;
+					last_stations[0] = all_stations[bestOrder[1]];
+					last_stations[1] = all_stations[bestOrder[2]];
+					find_best_order_of_2(r.pos,last_stations,bestOrder);
+					stack_reinit(&path);
+					target = last_stations[bestOrder[0]];
+					lee_run(r, target, &path);
+				}
+				break;
+			case 1:
+				if (!followPath_with_blockages(&r, &path,visited)) {
+					find_best_order_of_2(r.pos,last_stations,bestOrder);
+					target = last_stations[bestOrder[0]];
+					stack_reinit(&path);
+					lee_run(r, target, &path);
+				}
+				else {
+					//robot is in the station, manually spin
+					unexpanded_matrix[r.pos.x][r.pos.y]=0; //bugfix, somehow something was causing for a blockage to show up at station.
+					turnRight(&r);
+					r.dir=(r.dir+1)%4;
+					comm_await_crossing(2000);
+					comm_discard_sensor_data(1000);
+					visitedStations++;
+					stack_reinit(&path);
+					target = last_stations[bestOrder[1]];
+					lee_run(r, target, &path);
+				}
+				break;
+			case 2:
+				if (!followPath_with_blockages(&r,&path,visited)) {
+					stack_reinit(&path);
+					lee_run(r, target, &path);
+				}
+				else {
+					//robot is in the station, manually spin
+					unexpanded_matrix[r.pos.x][r.pos.y]=0; //bugfix, somehow something was causing for a blockage to show up at station.
+					turnRight(&r);
+					r.dir=(r.dir+1)%4;
+					comm_await_crossing(2000);
+					comm_discard_sensor_data(1000);
+					visitedStations++;
+				}
+				break;
+			case 3:
+				run=0;
+				break;
+			default: ;
+		}
+
+	}
+	stack_free(&path);
+	printMatrix_with_current_pos(visited,r);
+	printAllMoves();
+	comm_end_communication();
+}
+
+void find_best_order_of_3(cell start,cell stations[3],int bestOrder[3]) {
+	int minTotal = INT_MAX;
+
+	// test alle 6
+	for (int a = 0; a < 3; a++) {
+		for (int b = 0; b < 3; b++) {
+			if (b == a) continue;
+			for (int c = 0; c < 3; c++) {
+				if (c == a || c == b) continue;
+				int total = 0;
+				total += compute_path_length(start, stations[a]);
+				total += compute_path_length(stations[a], stations[b]);
+				total += compute_path_length(stations[b], stations[c]);
+				if (total < minTotal) {
+					minTotal = total;
+					bestOrder[0] = a;
+					bestOrder[1] = b;
+					bestOrder[2] = c;
+				}
+			}
+		}
+	}
+}
+
+void find_best_order_of_2(cell start,cell stations[2],int bestOrder[2]) {
+
+	int total1 = 0;
+	total1 += compute_path_length(start, stations[0]);
+	total1 += compute_path_length(stations[0], stations[1]);
+
+	int total2 = 0;
+	total2 += compute_path_length(start, stations[1]);
+	total2 += compute_path_length(stations[1], stations[0]);
+
+	if (total1 < total2) {
+		bestOrder[0] = 0;
+		bestOrder[1] = 1;
+	}
+	else {
+		bestOrder[0] = 1;
+		bestOrder[1] = 0;
+	}
+}
+
diff --git a/robot/challenges/challenge4.c b/robot/challenges/challenge4.c
new file mode 100644
index 0000000..a980817
--- /dev/null
+++ b/robot/challenges/challenge4.c
@@ -0,0 +1,168 @@
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "../../stack/stack.h"
+#include "../../cell/cell.h"
+#include "../../communication/communication.h"
+#include "../../lee-algorithm/lee-algorithm.h"
+#include "../../leelib/leelib.h"
+#include "../challenges/challenges.h"
+
+#define MAZE_SIZE 11
+
+extern int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE];
+extern cell neighbours[4];
+extern cell crossing_neighbours[4];
+int findNearestCrossing(robot r,int visited [MAZE_SIZE][ MAZE_SIZE],cell *result,int *crossing_counter);
+int compute_path_length(cell from, const cell to) ;
+
+
+void challenge_4(cell start) {
+	comm_init_communication();
+	cell finalStation,finalCrossing;
+	printf("Final destination? ");
+	readStation(&finalStation.x, &finalStation.y);
+	direction finalDirection = getStartDirection(finalStation); // direction away from the ending start
+
+	robot r;
+	r.pos = start;
+	r.dir = getStartDirection(start);
+	cell_add(&finalCrossing,finalStation,neighbours[getStartDirection(finalStation)]);
+	int visited[MAZE_SIZE][MAZE_SIZE] = {0};
+	memcpy(visited, unexpanded_matrix, sizeof(unexpanded_matrix));
+
+
+	cell result;
+	stack moves;
+	int crossing_counter=0,obstacle_counter=0;
+	stack_init(&moves);
+
+	stack first_move;
+	stack_init(&first_move);
+	stack_push(&first_move,neighbours[r.dir]);
+	followPath_with_blockages(&r,&first_move,visited);
+
+	while (findNearestCrossing(r,visited,&result,&crossing_counter)) {
+		lee_run(r,result,&moves);
+		if (!followPath_with_blockages(&r,&moves,visited)) { // ensure all is visited, no check for nr of obstacles because sometimes it creates bugs
+			obstacle_counter++;
+			if (validatePath(r,moves)) {
+				printf("following path \n");
+				followPath(&r,&moves,visited);
+			}
+			else {
+				crossing_counter--;
+			}
+		}
+		else { // if we know where all 12 blocks are, we go
+			followPath(&r,&moves,visited);
+		}
+		stack_reinit(&moves);
+		printf("Crossings:%d \n",crossing_counter);
+		//if (crossing_counter==25) {
+		//	break;
+		//}
+	}
+	lee_run(r,finalCrossing,&moves); // Go to crossing in front of the final destination
+	followPath(&r,&moves,visited);
+	stack_free(&moves);
+	spin(&r,finalDirection);
+	printMatrix_with_current_pos(visited,r);
+	parkBackwards(&r);
+	printMatrix_with_current_pos(visited,r);
+	printf("done");
+	printAllMoves();
+	comm_end_communication();
+
+}
+
+
+/**
+ * Function to find the nearest/best crossing to go to
+ * Steps:
+ * - Unvisited and without blocks
+ * - Unvisited but with a block
+ * - Visited
+ * In all cases forwards gets priority
+ * @param r robot
+ * @param visited array of all visited cells
+ * @param result crossing that was chosen as the best next possible move
+ * @param crossing_counter count amount of crossings
+ * @return 1 if found an unvisited crossing, 0 if all crossings visited.
+ */
+int findNearestCrossing(robot r,int visited [MAZE_SIZE][MAZE_SIZE],cell *result,int *crossing_counter) {
+	cell tempcell;
+	robot temp_robot;
+	temp_robot.pos = r.pos;
+	temp_robot.dir = r.dir;
+
+	if(!isValidCrossing(temp_robot.pos)){ // if robot is in a intersection, move it to crossing
+		cell_add(&temp_robot.pos,temp_robot.pos,neighbours[r.dir]);
+	}
+
+	// check for nearby unvisited crossings and without blockages
+	for (int i=0;i<4;i++) {
+		cell_add(&tempcell,temp_robot.pos,neighbours[(r.dir+i)%4]);
+		if (isInBound(tempcell) && unexpanded_matrix[tempcell.x][tempcell.y]!=-1) {
+			cell_add(&tempcell,temp_robot.pos,crossing_neighbours[(r.dir+i)%4]);
+			if (isValidCrossing(tempcell) && visited[tempcell.x][tempcell.y] == 0) {
+				*result= tempcell;
+				*crossing_counter+=1;
+				printf("nearby_unvisited \n");
+				return 1;
+			}
+		}
+	}
+
+	//find closest neighbour of neighbours
+	int min_distance = INT_MAX;
+	cell min_cell = (cell){0,0};
+
+	for (int i=0;i<4;i++) {
+		cell neighbour_crossing;
+		cell_add(&neighbour_crossing,temp_robot.pos,crossing_neighbours[i]);
+		for (int j=0;j<4;j++) {
+			cell_add(&tempcell,neighbour_crossing,neighbours[j]);
+			if (isInBound(tempcell) && unexpanded_matrix[tempcell.x][tempcell.y]!=-1) {
+				cell_add(&tempcell,tempcell,neighbours[j]);
+				if (isValidCrossing(tempcell) && visited[tempcell.x][tempcell.y] == 0) {
+					int tmp = compute_path_length(r.pos,tempcell);
+					if (tmp <= min_distance) {
+						min_distance=tmp;
+						min_cell = tempcell;
+					}
+				}
+			}
+		}
+	}
+	if (!cell_equals(min_cell, (cell){0,0})) {
+		*result=min_cell;
+		*crossing_counter+=1;
+		printf("neighb_of_neighb \n");
+		return 1;
+	}
+
+	min_distance = INT_MAX;
+	min_cell = (cell){0,0};
+	//find the closest unvisited crossing that isnt a neighbour of a neighbour.
+	for (int i=0;i<MAZE_SIZE;i++) {
+		for (int j=0;j<MAZE_SIZE;j++) {
+			tempcell = (cell) {i,j};
+			if (isValidCrossing(tempcell) && visited[i][j] == 0) {
+				int tmp = compute_path_length(r.pos,tempcell);
+					if (tmp <= min_distance) {
+						min_distance=tmp;
+						min_cell = tempcell;
+					}
+			}
+		}
+	}
+	if (!cell_equals(min_cell, (cell){0,0})) {
+		*result=min_cell;
+		*crossing_counter+=1;
+		printf("random_iterate \n");
+		return 1;
+	}
+	return 0;
+}
diff --git a/robot/challenges/challenges.h b/robot/challenges/challenges.h
new file mode 100644
index 0000000..f32385e
--- /dev/null
+++ b/robot/challenges/challenges.h
@@ -0,0 +1,11 @@
+#ifndef CHALLENGES_H
+#define CHALLENGES_H
+#include "../../cell/cell.h"
+
+
+void challenge_2();
+void challenge_3(cell start);
+void challenge_4(cell start);
+void challenge_4_old(cell start) ;
+#endif
+
diff --git a/robot/controller-moves.c b/robot/controller-moves.c
new file mode 100644
index 0000000..bf34fc2
--- /dev/null
+++ b/robot/controller-moves.c
@@ -0,0 +1,174 @@
+//
+// Created by nano on 5/14/25.
+//
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "robot.h"
+#include "../communication/communication.h"
+#include "../communication/utils.h"
+#include "../lee-algorithm/lee-algorithm.h"
+
+
+#define FORWARD 4
+#define BACKWARD 5//TBD
+#define TURN_LEFT 1
+#define TURN_RIGHT 2
+#define TURN_AROUND 3
+
+#define PARK 6
+
+#define CROSSING 32
+
+int firstMove = 1;
+/*
+ * FIRST MOVE:
+ * SEND: FWD
+ * RECV: ACK, SENSOR_DATA, CROSSING
+ * SEND: next move
+ */
+
+extern cell neighbours[4];
+extern cell crossing_neighbours[4];
+/* For any move:
+ * C SEND: LEFT / RIGHT / FWD
+ * C RECV: ACK , CROSSING, <SENSOR DATA>
+ * C SEND: NEXT INSTRUCTION
+ */
+void turnLeft(robot *r) {
+	comm_write_until_successful(TURN_LEFT, 1000);
+	r->dir = (r->dir + 3) % 4;
+}
+
+void turnRight(robot *r) {
+	comm_write_until_successful(TURN_RIGHT, 1000);
+	r->dir = (r->dir + 1) % 4;
+}
+
+void turnAround(robot *r) {
+/*
+	comm_write_until_successful(TURN_AROUND,1000);
+	r->dir = (r->dir + 2) % 4;*/
+	//THIJS:
+	turnRight(r);
+	comm_await_crossing(2000);
+	comm_discard_sensor_data(1000);
+	turnRight(r);
+}
+
+void forward(robot *r) {
+	comm_write_until_successful(FORWARD, 1000);
+	cell_add(&r->pos, r->pos, neighbours[r->dir]);
+}
+
+void backward(robot *r) {
+	comm_write_until_successful(BACKWARD,1000);
+	cell_add(&r->pos, r->pos, crossing_neighbours[(r->dir + 2) % 4]);
+	//printf("Doesnt exist rn");
+	//exit(-1);
+}
+
+void parkBackwards(robot *r) {
+	comm_write_until_successful(PARK,1000);
+	cell_add(&r->pos,r->pos,neighbours[(r->dir + 2) % 4]);
+}
+
+//BJORN CODE
+/*
+int first_move = 1;
+int followPath_with_blockages(robot *r, stack *path, int visited[MAZE_SIZE][MAZE_SIZE]) {
+
+	while (path->length > 0 ) {
+		int len=0;
+		cell current_move = stack_pop(path);
+		int result = move(r, current_move);
+		visited[r->pos.x][r->pos.y] = 5;
+		printMatrix_with_current_pos(visited, *r);
+
+		switch (result) {
+			case 0: //SPIN --> we expect sensor data
+				comm_get_distance_sensor(&len, 1000);
+				if (len != 0) {
+					len=(len-1)*2+1;
+					register_sensor_blockages(r, len, visited);
+					comm_await_crossing(2000);
+					return 0;
+				}
+				comm_await_crossing(2000);
+				break;
+			case 1: // FWD --> we do not expect sensor data, except fist move
+				comm_await_crossing(2000);
+				if (first_move) {
+					comm_get_distance_sensor(&len, 1000);
+					if (len != 0) {
+						len=(len-1)*2+1;
+						register_sensor_blockages(r, len, visited);
+						return 0;
+					}
+				}
+				break;
+			default : ;
+		}
+	}
+	return 1;
+}*/
+
+
+int followPath_with_blockages(robot *r, stack *path, int visited[MAZE_SIZE][MAZE_SIZE]) {
+	while (path->length > 0) {
+		int len = 0;
+		cell current_move = stack_pop(path);
+		int result = move(r, current_move);
+		visited[r->pos.x][r->pos.y] = 5;
+		switch (isValidCrossing(r->pos)) {
+			case 1:
+				comm_await_crossing(2000);
+				comm_get_distance_sensor(&len, 1000);
+				if (len != 0) {
+					//len=(len-1)*2+1;
+					register_sensor_blockages(r, len, visited);
+					return 0;
+				}
+				break;
+			case 0:
+				comm_await_crossing(2000);
+				comm_discard_sensor_data(1000);
+				break;
+			default: ;
+		}
+		printMatrix_with_current_pos(visited, *r);
+		if (result==0) { //spin
+			move(r, current_move); // advance forward
+			comm_await_crossing(2000);
+			comm_get_distance_sensor(&len, 1000);
+			if (len != 0) {
+				//len=(len-1)*2+1;
+				register_sensor_blockages(r, len, visited);
+				return 0;
+			}
+			printf("Continuing after spin cause no block \n");
+			printMatrix_with_current_pos(visited, *r);
+		}
+	}
+	return 1;
+}
+
+void printAllMoves() {
+}
+
+void comm_discard_sensor_data(int timeout) {
+	printf("DISCARDING DATA\n");
+	byte *b = malloc(sizeof(byte));
+	int run = 1;
+	//while (run) {
+		comm_blocking_read(b, 1, timeout);
+	//	for (int i = 1; i <= 5; i++) {
+	//		if (*b == (byte) i) {
+	//			run = 0;
+	//			break;
+	//		}
+	//	}
+	//}
+	printf("%d\n", *b);
+	free(b);
+}
diff --git a/robot/remote.c b/robot/remote.c
new file mode 100644
index 0000000..1feaa33
--- /dev/null
+++ b/robot/remote.c
@@ -0,0 +1,57 @@
+//
+// Created by nano on 5/14/25.
+//
+
+#include <ctype.h>
+#include <stdio.h>
+
+#include "robot.h"
+#include "../communication/communication.h"
+#include "../communication/utils.h"
+#include "../leelib/leelib.h"
+
+void simple_control() {
+	robot r;
+	printf("Where are we starting? ");
+	readStation(&r.pos.x,&r.pos.y);
+	r.dir=getStartDirection(r.pos);
+
+	comm_init_communication();
+	char in;
+	int run = 1;
+	while (run) {
+		printf("Move? ");
+		scanf("%c", &in);
+		switch (tolower(in)) {
+			case 'f':
+				printf("going forward\n");
+				forward(&r);
+				break;
+			case 'b':
+				printf("going backward\n");
+				backward(&r);
+				break;
+			case 'l':
+				printf("going left\n");
+				turnLeft(&r);
+				break;
+			case 'r':
+				printf("turning right\n");
+				turnRight(&r);
+				break;
+			case 'a':
+				printf("turning around\n");
+				turnAround(&r);
+				break;
+			case 'e':
+				printf("exiting\n");
+				run = 0;
+				break;
+			default:
+				break;
+		}
+		//byte b;
+		//comm_await_crossing(&b,50);
+	}
+	comm_end_communication();
+}
diff --git a/robot/robot.c b/robot/robot.c
new file mode 100644
index 0000000..5eb7b70
--- /dev/null
+++ b/robot/robot.c
@@ -0,0 +1,134 @@
+//
+// Created by nano on 5/9/25.
+//
+
+#include <stdio.h>
+
+#include "robot.h"
+
+#include "../lee-algorithm/lee-algorithm.h"
+
+extern int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE];
+extern const cell neighbours[4];
+char *arrow[4] = {"↑", "→", "↓", "←"};
+
+// Richting in tekst
+const char *directionToString(direction dir) {
+	switch (dir) {
+		case NORTH: return "NORTH";
+		case EAST: return "EAST";
+		case SOUTH: return "SOUTH";
+		case WEST: return "WEST";
+		default: return "UNKNOWN";
+	}
+}
+
+// Bepaal gewenste richting van current naar next
+
+int determineDirection(cell from, cell to) {
+	if (to.x == from.x - 1) return NORTH;
+	if (to.x == from.x + 1) return SOUTH;
+	if (to.y == from.y - 1) return WEST;
+	if (to.y == from.y + 1) return EAST;
+	return -1;
+}
+
+int determineDirectionFromMove(cell move) {
+	if (move.x == -1) return NORTH;
+	if (move.x == 1) return SOUTH;
+	if (move.y == -1) return WEST;
+	if (move.y == 1) return EAST;
+	return -1;
+}
+
+int getStartDirection(cell startCell) {
+	if (startCell.x == 0) return SOUTH;
+	if (startCell.x == MAZE_SIZE - 1) return NORTH;
+	if (startCell.y == 0) return EAST;
+	if (startCell.y == MAZE_SIZE - 1) return WEST;
+
+	//fprintf(stderr, "Warning: startCell is not on the maze edge!\n");
+	return NORTH; // fallback
+}
+
+void spin(robot *robot, direction desiredDirection) {
+	switch (robot->dir - desiredDirection) {
+		case -2:
+		case 2:
+			turnAround(robot);
+			break;
+		case 1:
+		case -3:
+			turnLeft(robot);
+			break;
+		case -1:
+		case 3:
+			turnRight(robot);
+			break;
+		case 0:
+		default:
+			break;
+	}
+}
+
+
+/**
+ * move the robot
+ * @param r robot
+ * @param move which move to make
+ * @return 1 if forward
+ * @return 0 if spin
+ */
+int move(robot *r, cell move) {
+	if (r->dir != (direction) determineDirectionFromMove(move)) {
+		spin(r, determineDirectionFromMove(move));
+		return 0;
+	}
+	forward(r);
+	return 1;
+}
+
+
+// Sensorinput: geeft 1–4 aan, blok in die richting, gemeten vanaf huidige robotpositie
+void register_sensor_blockages(robot* r, int sensorInput,int visited[MAZE_SIZE][MAZE_SIZE]) {
+
+	if (!isValidCrossing(r->pos)) {
+		printf("Waarschuwing: robot staat niet op een kruispunt (%d,%d)", r->pos.x, r->pos.y);
+	}
+
+	cell step = r->pos;
+	switch (r->dir) {
+		case NORTH: step.x -= sensorInput; break;
+		case EAST:  step.y += sensorInput; break;
+		case SOUTH: step.x += sensorInput; break;
+		case WEST:  step.y -= sensorInput; break;
+	}
+	if (step.x >= 1 && step.x < MAZE_SIZE-1 &&
+		step.y >= 1 && step.y < MAZE_SIZE-1 &&
+		((step.x%2==1 && step.y%2==0)|| (step.x%2==0 && step.y%2==1))) {
+		unexpanded_matrix[step.x][step.y] = -1;
+		visited[step.x][step.y] = -1;
+		printf("Blokkade geregistreerd op (%d, %d)", step.x, step.y);
+	}
+}
+
+void printMatrix_with_current_pos(int m[][MAZE_SIZE], robot r) {
+	//system("clear");
+	printf("\n");
+	for (int i = 0; i < MAZE_SIZE; i++) {
+		for (int j = 0; j < MAZE_SIZE; j++) {
+			if (r.pos.x == i && r.pos.y == j) {
+				printf("\033[31;47;1;4m %s \033[0m", arrow[r.dir]);
+				continue;
+			}
+			if (m[i][j] == 5) {
+				printf("\033[34;47;1m%3s\033[0m", "░░░");
+				continue;
+			}
+			printf("\033[%dm%3s\33[0m",m[i][j]<0?40:107, "░░░");
+		}
+		printf("\n");
+	}
+}
+
+
diff --git a/robot/robot.h b/robot/robot.h
new file mode 100644
index 0000000..0af09e4
--- /dev/null
+++ b/robot/robot.h
@@ -0,0 +1,58 @@
+//
+// Created by nano on 5/9/25.
+//
+
+#ifndef ROBOT_H
+#define ROBOT_H
+#include "../cell/cell.h"
+#include "../stack/stack.h"
+
+#define MAZE_SIZE 11
+
+typedef enum {
+	NORTH = 0,
+	EAST = 1,
+	SOUTH = 2,
+	WEST = 3
+} direction;
+
+
+typedef struct {
+	cell pos;
+	direction dir;
+} robot;
+
+void turnLeft(robot *r);
+
+void turnRight(robot *r);
+
+void turnAround(robot *r);
+
+void forward(robot *r);
+
+void backward(robot *r);
+
+const char *directionToString(direction dir);
+
+int determineDirection(cell from, cell to);
+
+int determineDirectionFromMove(cell move);
+
+int getStartDirection(cell startCell);
+
+void spin(robot *robot, direction desiredDirection);
+
+int move(robot *r, cell move);
+
+void printMatrix_with_current_pos(int m[][MAZE_SIZE], robot r);
+
+void register_sensor_blockages(robot* r, int sensorInput, int visited[MAZE_SIZE][MAZE_SIZE]);
+
+int followPath_with_blockages(robot *r, stack *path,int visited[MAZE_SIZE][MAZE_SIZE]);
+
+void simple_control();
+
+void printAllMoves();
+void parkBackwards(robot *r);
+void comm_discard_sensor_data(int timeout);
+#endif //ROBOT_H
diff --git a/robot/simple-simulator.c b/robot/simple-simulator.c
new file mode 100644
index 0000000..1cba272
--- /dev/null
+++ b/robot/simple-simulator.c
@@ -0,0 +1,66 @@
+#include <stdio.h>
+
+#define SIMULATION
+
+#include <ctype.h>
+
+#include "../leelib/leelib.h"
+#include "../lee-algorithm/lee-algorithm.h"
+#include "../cell/cell.h"
+
+extern int unexpanded_matrix[MAZE_SIZE][MAZE_SIZE];
+extern const cell neighbours[4];
+
+
+void addBlock(robot r, direction dir, cell targetCell, stack *s);
+
+void simple_control() { //TODO: OUTDATED, rewrite if needed.
+	/* read the starting and end station.*/
+	cell startCell, targetCell;
+	printf("STARTING AND ENDING STATION: ");
+	readStation(&startCell.x, &startCell.y);
+	readStation(&targetCell.x, &targetCell.y);
+
+	robot r;
+	r.dir = getStartDirection(startCell);
+	r.pos = startCell;
+	stack s;
+	stack_init(&s);
+	lee_run(r, targetCell, &s);
+
+	while (s.length > 0) {
+		move(&r, stack_pop(&s));
+		printMatrix_with_current_pos(unexpanded_matrix, r);
+
+		printf("BLOCKAGE: ");
+		char input;
+		scanf("%c", &input);
+		switch (tolower(input)) {
+			case 'n':
+				addBlock(r, NORTH, targetCell, &s);
+				break;
+			case 's':
+				addBlock(r, SOUTH, targetCell, &s);
+				break;
+			case 'e':
+				addBlock(r, EAST, targetCell, &s);
+				break;
+			case 'w':
+				addBlock(r, WEST, targetCell, &s);
+				break;
+			default:
+				break;
+		}
+	}
+	stack_free(&s);
+}
+
+void addBlock(robot r, direction dir, cell targetCell, stack *s) {
+	cell block;
+	cell_add(&block, r.pos, neighbours[dir]);
+	unexpanded_matrix[block.x][block.y] = -2; // putting -2 makes it not work???
+	if (!validatePath(r, *s)) {
+		stack_reinit(s);
+		lee_run(r, targetCell, s);
+	}
+}
diff --git a/robot/simulator-moves.c b/robot/simulator-moves.c
new file mode 100644
index 0000000..323175a
--- /dev/null
+++ b/robot/simulator-moves.c
@@ -0,0 +1,110 @@
+//
+// Created by nano on 5/14/25.
+//
+// Functies om de richting aan te passen
+#include <ctype.h>
+#include <stdio.h>
+
+#include "robot.h"
+#include "../lee-algorithm/lee-algorithm.h"
+
+//Dummy moves for the simulator / when a machine with libserialport is unavailable.
+
+extern cell neighbours[4];
+//extern cell crossing_neighbours[4];
+
+char *moves[100];
+int indx;
+
+void turnLeft(robot *r) {
+	r->dir = (r->dir + 3) % 4;
+	moves[indx] = "\33[1;102mL\33[0m";
+	indx++;
+}
+
+void turnRight(robot *r) {
+	r->dir = (r->dir + 1) % 4;
+	moves[indx] = "\33[1;101mR\33[0m";
+	indx++;
+}
+
+void turnAround(robot *r) {
+	r->dir = (r->dir + 2) % 4;
+	moves[indx] = "\33[1;103mS\33[0m";
+	indx++;
+}
+
+void forward(robot *r) {
+	cell_add(&r->pos, r->pos, neighbours[r->dir]);
+	moves[indx] = "\33[1;105mF\33[0m";
+	indx++;
+}
+
+void backward(robot *r) {
+	cell_add(&r->pos, r->pos, neighbours[(r->dir + 2) % 4]);
+	moves[indx] = "\33[1;44mB\33[0m";
+	indx++;
+}
+
+
+int followPath_with_blockages(robot *r, stack *path,int visited[MAZE_SIZE][MAZE_SIZE]) {
+	while (path->length > 0) {
+		cell current_move = stack_pop(path);
+		int result = move(r,current_move);
+		visited[r->pos.x][r->pos.y] = 5;
+		printMatrix_with_current_pos(visited,*r);
+		if (isValidCrossing(r->pos)) {
+			printf("ADD BLOCKAGE? (Y/N) ");
+			char input[10];
+			scanf("%s", input);
+			printf("\n");
+			if (tolower(input[0]) == 'y' ){
+				printf("HOW FAR? (1-4) ");
+				int len;
+				scanf("%d",&len);
+				printf("\n");
+				len=(len-1)*2+1;
+				register_sensor_blockages(r,len,visited);
+				return 0;
+			}
+		}
+		if (result == 0) {
+			move(r,current_move);
+			visited[r->pos.x][r->pos.y] = 5;
+			printMatrix_with_current_pos(visited,*r);
+			if (isValidCrossing(r->pos)) {
+				printf("ADD BLOCKAGE? (Y/N) ");
+				char input[10];
+				scanf("%s", input);
+				printf("\n");
+				if (tolower(input[0]) == 'y' ){
+					printf("HOW FAR? (1-4) ");
+					int len;
+					scanf("%d",&len);
+					printf("\n");
+					len=(len-1)*2+1;
+					register_sensor_blockages(r,len,visited);
+					return 0;
+				}
+			}
+		}
+	}
+	return 1;
+}
+
+void printAllMoves() {
+	printf("\n");
+	for (int i = 0; i < indx; i++) {
+		printf("%s",moves[i]);
+	}
+	printf("\n");
+}
+
+void parkBackwards(robot *r) {
+	backward(r);
+}
+
+void comm_discard_sensor_data(int timeout){}
+void comm_await_crossing(){}
+void comm_init_communication(){}
+void comm_end_communication(){}
diff --git a/stack/stack.c b/stack/stack.c
new file mode 100644
index 0000000..31b5db5
--- /dev/null
+++ b/stack/stack.c
@@ -0,0 +1,83 @@
+//
+// Created by nano on 4/30/25.
+//
+
+
+#include <stdlib.h>
+#include <string.h>
+#include "stack.h"
+
+#include <limits.h>
+#include <math.h>
+
+void stack_init(stack *stack) {
+	stack -> length = 0;
+	stack -> size = 1;
+	stack -> data = calloc(stack->size,sizeof(cell));
+}
+
+void stack_free(stack *stack) {
+	free(stack -> data);
+	stack->size = 0;
+	stack->length = 0;
+}
+
+void stack_reinit(stack *stack) {
+	stack_free(stack);
+	stack_init(stack);
+}
+
+void stack_expand(stack *stack) {
+	stack -> size = stack -> size *2;
+	cell *new_data = calloc(stack -> size ,sizeof(cell));
+	memcpy(new_data, stack -> data, stack -> size/2 * sizeof(cell));
+	free(stack -> data);
+	stack -> data = new_data;
+}
+
+void stack_push(stack *stack, cell c) {
+	if (stack -> length + 1 == stack -> size) {
+		stack_expand(stack);
+	}
+	stack -> data[stack -> length++] = c;
+}
+
+void stack_shrink(stack *stack) {
+	stack -> size = stack -> size / 2;
+	cell *new_data = calloc(stack -> size , sizeof(cell));
+	memcpy(new_data, stack -> data, stack -> size * sizeof(cell));
+	free(stack -> data);
+	stack -> data = new_data;
+}
+
+cell stack_pop(stack *stack) {
+	if (stack -> length > 0) {
+		const cell c = stack -> data[stack -> length - 1];
+		if ((stack->length - 1) == (stack->size / 2) && stack -> size/2 !=0) {
+			stack_shrink(stack);
+		}
+		stack -> length--;
+		return c;
+	}
+	return (cell) {INT_MAX,INT_MAX};
+}
+
+void stack_invert(stack *stack) {
+	cell *inv_data = calloc(stack -> size , sizeof(cell));
+	for (int i=0;i<stack->length;i++)
+		inv_data[stack->length -1 - i] = stack->data[i];
+	free(stack -> data);
+	stack -> data = inv_data;
+}
+
+void stack_append(const stack *from, stack *to) {
+	const int size = (int) pow(2, ceil(log2(to->length + from->length)));
+	// power of 2 which has enough space to hold all the contents of both stacks.
+	cell *new_data = calloc(size,sizeof(cell));
+	memcpy(new_data, to->data, to->length * sizeof(cell));
+	memcpy(new_data+to->length, from -> data, from -> length * sizeof(cell));
+	free(to->data);
+	to->data = new_data;
+	to->length = to->length + from -> length;
+	to->size = size;
+}
\ No newline at end of file
diff --git a/stack/stack.h b/stack/stack.h
new file mode 100644
index 0000000..601a941
--- /dev/null
+++ b/stack/stack.h
@@ -0,0 +1,26 @@
+//
+// Created by nano on 4/30/25.
+//
+
+#ifndef STACK_H
+#define STACK_H
+
+#include "../cell/cell.h"
+
+
+typedef struct stack {
+	cell *data;
+	int length;
+	int size;
+} stack;
+
+void stack_init(stack *stack) ;
+void stack_free(stack *stack) ;
+void stack_reinit(stack *stack);
+
+void stack_push(stack *stack, cell c) ;
+cell stack_pop(stack *stack) ;
+void stack_invert(stack *stack);
+void stack_append(const stack *from, stack *to);
+
+#endif //STACK_H
diff --git a/stack/stack_test.c b/stack/stack_test.c
new file mode 100644
index 0000000..9f716f8
--- /dev/null
+++ b/stack/stack_test.c
@@ -0,0 +1,56 @@
+//
+// Created by nano on 4/30/25.
+//
+#include <stdio.h>
+#include "stack.h"
+
+
+/**
+ * Quick file to test all functions of the implemented stack.
+ */
+int main(void){
+	int ret =1;
+	stack stk;
+	stack_init(&stk);
+
+	BEGIN:
+	for (int i=0;i<=100;i++) {
+		cell c;
+		c.x = i;
+		c.y = 100-i;
+		stack_push(&stk, c);
+		printf("pushed: %d,%d\n",c.x,c.y);
+	}
+	stack_invert(&stk);
+
+	if (ret) {
+		printf("2nd run \n");
+		ret=0;
+		stack_reinit(&stk);
+		goto BEGIN;
+	}
+	stack_free(&stk);
+
+	printf("Append Test \n");
+	stack s1,s2;
+	stack_init(&s1);
+	stack_init(&s2);
+	for (int i=0;i<100;i++) {
+		stack_push(&s1,(cell){i,i});
+		stack_push(&s2,(cell){i,i});
+	}
+	for (int i=0;i<80;i++) {
+		stack_pop(&s1);
+	}
+	printf("s1 size: %d, s1 len: %d \ns2 size: %d, s2 len: %d \n",s1.size,s1.length,s2.size,s2.length);
+	stack_append(&s1,&s2);
+	printf("s2 size: %d, s2 len: %d \n",s2.size,s2.length);
+	while (s2.length) {
+		cell c = stack_pop(&s2);
+		printf("popped: %d,%d\n", c.x,c.y);
+	}
+	stack_free(&s1);
+	stack_free(&s2);
+
+	return 0;
+}
\ No newline at end of file
diff --git a/todo.md b/todo.md
new file mode 100644
index 0000000..9267133
--- /dev/null
+++ b/todo.md
@@ -0,0 +1,20 @@
+# TODO
+
+- [x] implement direction
+- [x] make lee alg prefer straight line moves over turns (involves direction i would say)
+- [x] make the code output a set of instructions for the robot.
+- [x] replace the stuff in main.c with an "emulator" that will behave like the robot, so we can test without being
+  forced to have the robot connected at all times.
+- [x] think of strategies for the different challenges
+- [x] implement and optimize said strategies
+- [x] test all challenges
+
+### Instructions for the robot are gonna be like:
+
+- Forward x
+- Spin left x
+- spin right x
+- 180 deg turn x
+- backward x
+- (any other moves we can implement on the robot to make it faster)
+- spin might have to be a routine because of the placement of the sensor ?
\ No newline at end of file