Notes

float cellSize = 40; // Size of each cell in the grid
float gridSize = 20; // Number of cells in each row and column
float gridOffsetX = 20; // Offset of the grid from the left side
float gridOffsetY = 20; // Offset of the grid from the top side
float gridBottomOffsetY = 20; // Offset of the grid from the bottom side

float snakeX; // X-coordinate of the snake's head
float snakeY; // Y-coordinate of the snake's head
float snakeSpeed = cellSize; // Speed of the snake's movement
float snakeDirectionX = 1; // Initial movement direction of the snake along the x-axis
float snakeDirectionY = 0; // Initial movement direction of the snake along the y-axis

int score = 0; // Player's score
boolean gameOver = false; // Flag to track if the game is over
boolean gameStarted = false; // Flag to track if the game has started
boolean gameWon = false; // Flag to track if the game has been won

ArrayList<PVector> snakeBody; // List to store the coordinates of the snake's body
int appleX; // X-coordinate of the apple
int appleY; // Y-coordinate of the apple

void setup() {
size(800, 800); // Set canvas size to 800x800 pixels
frameRate(5); // Set the frame rate to 5 frames per second
snakeX = gridOffsetX + cellSize * floor(gridSize / 2); // Set the initial x-coordinate of the snake's head
snakeY = gridOffsetY + cellSize * floor(gridSize / 2); // Set the initial y-coordinate of the snake's head

snakeBody = new ArrayList<PVector>(); // Initialize the snake's body
snakeBody.add(new PVector(snakeX, snakeY)); // Add the initial position of the snake's head
score = 0; // Initialize the player's score
}

void draw() {
background(255); // Set background color to white

if (gameStarted) {
drawGrid(); // Call the function to draw the chequered grid

if (!gameOver && !gameWon) {
moveSnake(); // Call the function to move the snake
checkCollisions(); // Check for collisions with boundaries, apples, and self
}

drawSnake(); // Call the function to draw the snake
drawApple(); // Call the function to draw the apple

if (gameOver) {
displayGameOver(); // Display the game over screen
} else if (gameWon) {
displayGameWon(); // Display the game won screen
}

displayScore(); // Display the player's score
} else {
displayWelcomeScreen(); // Display the welcome screen
}
}


void keyPressed() {
if (!gameStarted) {
if (key == CODED && keyCode == SHIFT) { // Start the game if SHIFT key is pressed
startGame();
}
} else {
if (keyCode == UP && snakeDirectionY != 1) { // Avoid the snake reversing its direction instantly
snakeDirectionX = 0;
snakeDirectionY = -1;
} else if (keyCode == DOWN && snakeDirectionY != -1) {
snakeDirectionX = 0;
snakeDirectionY = 1;
} else if (keyCode == LEFT && snakeDirectionX != 1) {
snakeDirectionX = -1;
snakeDirectionY = 0;
} else if (keyCode == RIGHT && snakeDirectionX != -1) {
snakeDirectionX = 1;
snakeDirectionY = 0;
} else if (keyCode == SHIFT && (gameOver || gameWon)) { // Restart the game if SHIFT key is pressed after game over or game won
resetGame();
}
}
}

void moveSnake() {
float newX = snakeBody.get(0).x + snakeDirectionX * snakeSpeed; // Calculate the new x-coordinate of the snake's head
float newY = snakeBody.get(0).y + snakeDirectionY * snakeSpeed; // Calculate the new y-coordinate of the snake's head

// Check if the new position is within the specified boundaries
if (newX >= 20 && newX < 780 && newY >= 60 && newY < 780) {
// Create a new head position
PVector newHead = new PVector(newX, newY);

// Add the new head position to the beginning of the snake's body
snakeBody.add(0, newHead);

// Remove the tail of the snake if it hasn't eaten an apple
if (!hasEatenApple()) {
snakeBody.remove(snakeBody.size() - 1);
}
} else {
gameOver = true; // Set the game over flag to true if the snake moves outside the boundaries
}
}


void drawGrid() {
// Draw the chequered grid
for (int i = 0; i < gridSize; i++) { // Rows
for (int j = 0; j < gridSize; j++) { // Columns
float x = gridOffsetX + j * cellSize; // Calculate x-coordinate of the cell
float y = gridOffsetY + i * cellSize; // Calculate y-coordinate of the cell

if ((i + j) % 2 == 0) {
if (x >= 20 && x < 780 && y >= 60 && y < 780) { // Check if the cell is within the specified boundaries
drawCell(x, y, true); // Even cells have a different color
}
} else {
if (x >= 20 && x < 780 && y >= 60 && y < 780) { // Check if the cell is within the specified boundaries
drawCell(x, y, false); // Odd cells have a different color
}
}
}
}

// Draw the boundaries
stroke(0);
strokeWeight(2);
line(20, 60, 780, 60); // Top boundary
line(780, 60, 780, 780); // Right boundary
line(780, 780, 20, 780); // Bottom boundary
line(20, 780, 20, 60); // Left boundary
}

void drawCell(float x, float y, boolean colour) {
// Draw a single cell
if (colour) {
fill(200); // Set color to gray for even cells
} else {
fill(100); // Set color to dark gray for odd cells
}
stroke(0); // Set border color to black
rect(x, y, cellSize, cellSize); // Draw the cell as a square
}

void drawSnake() {
for (int i = 0; i < snakeBody.size(); i++) {
float x = snakeBody.get(i).x;
float y = snakeBody.get(i).y;

if (i == 0) {
fill(255, 0, 0); // Set color of the snake's head (red)
} else {
fill(0); // Set color of the snake's body (black)
}

rect(x, y, cellSize, cellSize); // Draw each segment of the snake's body
}
}


void placeApple() {
int maxGridIndex = int(gridSize) - 1;

// Generate random coordinates for the apple within the specified boundaries
appleX = int(random(1, maxGridIndex)) * int(cellSize) + int(gridOffsetX);
appleY = int(random(1, maxGridIndex)) * int(cellSize) + int(gridOffsetY);
}

void drawApple() {
fill(255, 0, 0); // Set color of the apple to red
ellipse(appleX + cellSize / 2, appleY + cellSize / 2, cellSize, cellSize); // Draw the apple as a circle
}

boolean hasEatenApple() {
// Check if the snake's head is overlapping with the apple
return snakeBody.get(0).x == appleX && snakeBody.get(0).y == appleY;
}

void checkCollisions() {
// Check if the snake has collided with the boundaries or itself
if (snakeBody.get(0).x < 20 || snakeBody.get(0).x >= 780 ||
snakeBody.get(0).y < 60 || snakeBody.get(0).y >= 780 ||
isCollidingWithSelf()) {
gameOver = true; // Set the game over flag to true
}

if (hasEatenApple()) {
score++; // Increase the player's score
placeApple(); // Place a new apple
if (score == 10) {
gameWon = true; // Set the game won flag to true
}
}
}

boolean isCollidingWithSelf() {
// Check if the snake's head is colliding with any part of its body
for (int i = 1; i < snakeBody.size(); i++) {
if (snakeBody.get(0).x == snakeBody.get(i).x && snakeBody.get(0).y == snakeBody.get(i).y) {
return true;
}
}
return false;
}

void displayWelcomeScreen() {
background(0); // Set background color to black
textAlign(CENTER, CENTER);
fill(255); // Set text color to white
textSize(32);
text("Welcome to Snake Game!", width / 2, height / 2 - 50);
textSize(18);
text("Use arrow keys to move the snake", width / 2, height / 2);
text("Press SHIFT to start the game", width / 2, height / 2 + 50);
}

void displayGameOver() {
fill(0, 200); // Set the background color to transparent black
rect(0, 0, width, height); // Draw a rectangle covering the entire screen

textAlign(CENTER, CENTER);
fill(255); // Set text color to white
textSize(32);
text("Game Over!", width / 2, height / 2 - 50);
textSize(18);
text("Press SHIFT to restart", width / 2, height / 2);
}

void displayGameWon() {
fill(0, 200); // Set the background color to transparent black
rect(0, 0, width, height); // Draw a rectangle covering the entire screen

textAlign(CENTER, CENTER);
fill(255); // Set text color to white
textSize(32);
text("Congratulations!", width / 2, height / 2 - 50);
textSize(18);
text("You won the game!", width / 2, height / 2);
text("Press SHIFT to restart", width / 2, height / 2 + 50);
}

void displayScore() {
textAlign(LEFT, TOP);
fill(0); // Set text color to black
textSize(18);
text("Score: " + score, 20, 20); // Display the score at the top left corner
}

void startGame() {
gameStarted = true; // Set the game started flag to true
score = 0; // Reset the player's score
snakeBody.clear(); // Clear the snake's body
snakeBody.add(new PVector(snakeX, snakeY)); // Add the initial position of the snake's head
placeApple(); // Place the apple
snakeDirectionX = 1; // Reset the movement direction of the snake
snakeDirectionY = 0;
gameOver = false; // Reset the game over flag
gameWon = false; // Reset the game won flag
}

void resetGame() {
gameStarted = false; // Set the game started flag to false
}