```html
Snake
Snake
Score: 0
High: 0
Arrow keys or WASD to move · Space to start/pause · R to restart
```
```typescript
type Cell = { x: number; y: number };
type Direction = { x: number; y: number };
const GRID = 20;
const CELL = 20;
const INITIAL_TICK_MS = 150;
const MIN_TICK_MS = 60;
const SPEEDUP_EVERY = 5; // apples
const SPEEDUP_DELTA = 10; // ms
class Game {
private canvas: HTMLCanvasElement;
private ctx: CanvasRenderingContext2D;
private scoreEl: HTMLElement;
private highEl: HTMLElement;
// Game State
private snake: Cell[];
private dir: Direction;
private pendingDir: Direction | null;
private food: Cell;
private score: number;
private high: number;
private tickMs: number;
private alive: boolean;
private started: boolean;
private paused: boolean;
constructor(canvas: HTMLCanvasElement, scoreEl: HTMLElement, highEl: HTMLElement) {
this.canvas = canvas;
this.ctx = canvas.getContext('2d', '2d');
this.scoreEl = scoreEl;
this.highEl = highEl;
// Initial State Setup
this.snake = [
{ x: 10, y: 10 }, // Head
{ x: 9, y: 10 }, // Body 1
{ x: 8, y: 10 } // Body 2
];
this.dir = { x: 1, y: 0 }; // Initial direction: Right
this.pendingDir = null;
this.food = { x: 0, y: 0 }; // Placeholder
this.score = 0;
this.high = 0;
this.tickMs = INITIAL_TICK_MS;
this.alive = true;
this.started = false;
this.paused = true; // Starts paused
this.loadHighScore();
this.setupListeners();
this.draw();
}
private loadHighScore(): void {
const storedHigh = localStorage.getItem('snake.high');
if (storedHigh !== null) {
this.high = parseInt(storedHigh, 10);
}
this.highEl.textContent = `High: ${this.high}`;
}
private saveHighScore(): void {
if (this.score > this.high) {
this.high = this.score;
localStorage.setItem('snake.high', this.high.toString());
this.highEl.textContent = `High: ${this.high}`;
}
}
private setupListeners(): void {
window.addEventListener('keydown', this.handleInput.bind(this));
}
private handleInput(e: KeyboardEvent): void {
const newDir = this.getNewDirection(e);
if (newDir) {
// Reverse-into-self prevention
if (newDir.x !== -this.dir.x || newDir.y !== -this.dir.y) {
this.pendingDir = newDir;
}
}
}
private getNewDirection(e: KeyboardEvent): Direction | null {
switch (e.key) {
case 'ArrowUp':
case 'w':
return { x: 0, y: -1 };
case 'ArrowDown':
case 's':
return { x: 0, y: 1 };
case 'ArrowLeft':
case 'a':
return { x: -1, y: 0 };
case 'ArrowRight':
case 'd':
return { x: 1, y: 0 };
case ' ':
if (!this.started) {
this.start();
} else {
this.togglePause();
}
return null; // Space handled separately
case 'r':
this.restart();
return null;
default:
return null;
}
}
public start(): void {
if (!this.started) {
this.started = true;
this.paused = false;
this.tick();
}
}
public togglePause(): void {
if (!this.started) return;
this.paused = !this.paused;
if (this.paused) {
// Pause the interval if it's running
clearInterval(this.intervalId);
} else {
// Resume the interval
this.tick();
}
this.draw();
}
public restart(): void {
// Full reset to initial state, paused-before-start
this.snake = [
{ x: 10, y: 10 },
{ x: 9, y: 10 },
{ x: 8, y: 10 }
];
this.dir = { x: 1, y: 0 };
this.pendingDir = null;
this.score = 0;
this.tickMs = INITIAL_TICK_MS;
this.alive = true;
this.started = false;
this.paused = true;
this.loadHighScore();
this.draw();
}
private placeFood(): void {
let newFood: Cell;
do {
newFood = {
x: Math.floor(Math.random() * GRID),
y: Math.floor(Math.random() * GRID)
};
} while (this.snake.some(segment => segment.x === newFood.x && segment.y === newFood.y));
this.food = newFood;
}
private tick(): void {
if (!this.alive) return;
// 1. Update Direction
if (this.pendingDir) {
this.dir = this.pendingDir;
this.pendingDir = null;
}
// 2. Calculate New Head Position
const head = this.snake[0];
const newHead: Cell = { x: head.x + this.dir.x, y: head.y + this.dir.y };
// 3. Check Game Over Conditions (Walls)
if (newHead.x < 0 || newHead.x >= GRID || newHead.y < 0 || newHead.y >= GRID) {
this.alive = false;
this.gameOver();
return;
}
// 4. Check Self Collision (excluding tail chase)
// Check against body segments (excluding the tail, which is allowed to be chased)
for (let i = 1; i < this.snake.length - 1; i++) {
if (newHead.x === this.snake[i].x && newHead.y === this.snake[i].y) {
this.alive = false;
this.gameOver();
return;
}
}
// 5. Move Snake
this.snake.unshift(newHead);
// 6. Check Food Consumption
if (newHead.x === this.food.x && newHead.y === this.food.y) {
this.score++;
this.placeFood();
this.updateSpeed();
} else {
// If no food eaten, remove the tail
this.snake.pop();
}
}
private updateSpeed(): void {
const newTickMs = Math.max(MIN_TICK_MS, INITIAL_TICK_MS - Math.floor(this.score / SPEEDUP_EVERY) * SPEEDUP_DELTA);
if (newTickMs !== this.tickMs) {
this.tickMs = newTickMs;
// Restart the interval with the new speed
clearInterval(this.intervalId);
this.intervalId = setInterval(this.tick, this.tickMs);
}
}
private gameOver(): void {
this.started = false;
this.paused = true;
clearInterval(this.intervalId);
this.draw(); // Final draw
}
private draw(): void {
this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
// Draw Background
this.ctx.fillStyle = '#000';
this.ctx.fillRect(0, 0, this.canvas.width, this.canvas.height);
// Draw Food
this.ctx.fillStyle = '#c0392b';
this.ctx.fillRect(this.food.x * CELL, this.food.y * CELL, CELL, CELL);
// Draw Snake
this.snake.forEach((segment, index) => {
if (index === 0) {
// Head
this.ctx.fillStyle = '#7ed957'; // Brighter green
} else {
// Body
this.ctx.fillStyle = '#3aa635'; // Darker green
}
this.ctx.fillRect(segment.x * CELL, segment.y * CELL, CELL, CELL);
});
// Draw Pause/Game Over Overlay
if (!this.started) {
this.drawPauseOverlay();
} else if (!this.alive) {
this.drawGameOverOverlay();
} else if (this.paused) {
this.drawPausedOverlay();
}
}
private drawPauseOverlay(): void {
const centerX = this.canvas.width / 2;
const centerY = this.canvas.height / 2;
this.ctx.fillStyle = '#fff';
this.ctx.font = '20px sans-serif';
this.ctx.textAlign = 'center';
this.ctx.fillText('Paused', centerX, centerY);
}
private drawGameOverOverlay(): void {
const centerX = this.canvas.width / 2;
const centerY = this.canvas.height / 2;
this.ctx.fillStyle = '#fff';
this.ctx.font = '20px sans-serif';
this.ctx.textAlign = 'center';
this.ctx.fillText('Game Over — press R to restart', centerX, centerY);
}
public run(): void {
// Start the initial interval
this.intervalId = setInterval(this.tick, this.tickMs);
}
}
// --- Initialization ---
const canvas = document.getElementById('game') as HTMLCanvasElement;
const scoreEl = document.getElementById('score') as HTMLElement;
const highEl = document.getElementById('high') as HTMLElement;
const game = new Game(canvas, scoreEl, highEl);
// Start the game loop immediately (it will be paused by default)
game.run();
```