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;
const SPEEDUP_DELTA = 10;
const COLOR_BG = "#000";
const COLOR_BODY = "#3aa635";
const COLOR_HEAD = "#7ed957";
const COLOR_FOOD = "#c0392b";
const COLOR_TEXT = "#fff";
const HIGH_KEY = "snake.high";
class Game {
private canvas: HTMLCanvasElement;
private ctx: CanvasRenderingContext2D;
private scoreEl: HTMLElement;
private highEl: HTMLElement;
private snake!: Cell[];
private dir!: Direction;
private pendingDir: Direction | null = null;
private food!: Cell;
private score!: number;
private high!: number;
private tickMs!: number;
private alive!: boolean;
private started!: boolean;
private paused!: boolean;
private timer: number | null = null;
constructor(canvas: HTMLCanvasElement, scoreEl: HTMLElement, highEl: HTMLElement) {
this.canvas = canvas;
const ctx = canvas.getContext("2d");
if (!ctx) throw new Error("no 2d context");
this.ctx = ctx;
this.scoreEl = scoreEl;
this.highEl = highEl;
this.high = localStorage.getItem(HIGH_KEY) ? parseInt(localStorage.getItem(HIGH_KEY)!) : 0;
this.resetState();
this.render();
}
/** Begin the game on first Space press: started=true, paused=false, start the tick interval. No-op if already started. */
start(): void {
if (!this.started) {
this.started = true;
this.paused = false;
this.timer = setInterval(() => this.step(), this.tickMs);
}
}
/** Toggle pause on/off during a running game. If not yet started, behave like start(). When unpausing, re-arm the interval. When pausing, clear it. */
togglePause(): void {
if (this.started) {
this.paused = !this.paused;
if (this.paused) {
clearInterval(this.timer!);
this.timer = null;
} else {
this.timer = setInterval(() => this.step(), this.tickMs);
}
} else {
this.start();
}
}
/** Full reset to the initial paused-before-start state, then render. Clears the tick interval if running. */
restart(): void {
clearInterval(this.timer!);
this.timer = null;
this.resetState();
this.render();
}
/** Apply pendingDir if it is not the opposite of the current dir, then move the snake one cell, detect wall/self collisions, handle food, and render. Called once per tick interval. */
private step(): void {
if (this.pendingDir) {
if (!(this.pendingDir.x === -this.dir.x && this.pendingDir.y === -this.dir.y)) {
this.dir = this.pendingDir;
this.pendingDir = null;
}
}
const head: Cell = { x: this.snake[0].x + this.dir.x, y: this.snake[0].y + this.dir.y };
this.snake.unshift(head);
if (this.wouldCollide(head, false)) {
this.alive = false;
clearInterval(this.timer!);
this.timer = null;
this.render();
return;
}
if (this.food.x === head.x && this.food.y === head.y) {
this.score++;
if (this.score > this.high) {
this.high = this.score;
localStorage.setItem(HIGH_KEY, this.high.toString());
}
this.updateScoreDom();
this.spawnFood();
if (this.score % SPEEDUP_EVERY === 0) {
this.tickMs = Math.max(this.tickMs - SPEEDUP_DELTA, MIN_TICK_MS);
clearInterval(this.timer!);
this.timer = setInterval(() => this.step(), this.tickMs);
}
} else {
this.snake.pop();
}
this.render();
}
/** Set snake (length 3 at (10,10), (9,10), (8,10) moving right), reset dir/pendingDir/score/tickMs/alive/started/paused, spawn food. */
private resetState(): void {
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.updateScoreDom();
this.spawnFood();
}
/** Pick a random Cell that is not currently occupied by the snake. If no empty cell, treat as win (alive=false, render). */
private spawnFood(): void {
let emptyCells: Cell[] = [];
for (let y = 0; y < GRID; y++) {
for (let x = 0; x < GRID; x++) {
if (!this.snake.some(cell => cell.x === x && cell.y === y)) {
emptyCells.push({ x, y });
}
}
}
if (emptyCells.length === 0) {
this.alive = false;
clearInterval(this.timer!);
this.timer = null;
this.render();
} else {
this.food = emptyCells[Math.floor(Math.random() * emptyCells.length)];
}
}
/** Update the score and high DOM elements with "Score: N" / "High: N". */
private updateScoreDom(): void {
this.scoreEl.textContent = `Score: ${this.score}`;
this.highEl.textContent = `High: ${this.high}`;
}
/** Clear and redraw the board: black bg, food, snake body, snake head (distinct color). On not-yet-started, draw centered "Press Space to start". On paused (after first start), draw centered "Paused". On game-over, draw centered "Game Over — press R to restart". Text 20px sans-serif white, centered. */
private render(): void {
this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
this.ctx.fillStyle = COLOR_BG;
this.ctx.fillRect(0, 0, this.canvas.width, this.canvas.height);
if (!this.alive) {
this.ctx.font = '20px sans-serif';
this.ctx.fillStyle = COLOR_TEXT;
this.ctx.textAlign = 'center';
this.ctx.textBaseline = 'middle';
if (this.started) {
this.ctx.fillText('Game Over — press R to restart', this.canvas.width / 2, this.canvas.height / 2);
} else {
this.ctx.fillText('Press Space to start', this.canvas.width / 2, this.canvas.height / 2);
}
} else {
this.ctx.fillStyle = COLOR_FOOD;
this.ctx.fillRect(this.food.x * CELL, this.food.y * CELL, CELL, CELL);
for (let i = 0; i < this.snake.length; i++) {
const cell = this.snake[i];
this.ctx.fillStyle = i === 0 ? COLOR_HEAD : COLOR_BODY;
this.ctx.fillRect(cell.x * CELL, cell.y * CELL, CELL, CELL);
}
if (this.paused) {
this.ctx.font = '20px sans-serif';
this.ctx.fillStyle = COLOR_TEXT;
this.ctx.textAlign = 'center';
this.ctx.textBaseline = 'middle';
this.ctx.fillText('Paused', this.canvas.width / 2, this.canvas.height / 2);
}
}
}
/** True iff `cell` lies inside the grid AND is not occupied by `snake` (excluding the soon-to-vacate tail when not growing). */
private wouldCollide(cell: Cell, willGrow: boolean): boolean {
return cell.x < 0 || cell.x >= GRID || cell.y < 0 || cell.y >= GRID || (!willGrow && this.snake.some(snakeCell => snakeCell.x === cell.x && snakeCell.y === cell.y));
}
setPendingDir(dir: Direction): void {
this.pendingDir = dir;
}
}
// ---- top-level wiring (fill in) ----
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);
window.addEventListener('keydown', (e) => {
switch (e.key) {
case 'ArrowUp':
case 'w':
game.setPendingDir({ x: 0, y: -1 });
break;
case 'ArrowDown':
case 's':
game.setPendingDir({ x: 0, y: 1 });
break;
case 'ArrowLeft':
case 'a':
game.setPendingDir({ x: -1, y: 0 });
break;
case 'ArrowRight':
case 'd':
game.setPendingDir({ x: 1, y: 0 });
break;
case ' ':
game.togglePause();
break;
case 'r':
game.restart();
break;
default:
return;
}
e.preventDefault();
});
```