```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 = Number(localStorage.getItem(HIGH_KEY)) || 0;
this.resetState();
this.updateScoreDom();
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) return;
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.start();
return;
}
if (this.paused) {
this.paused = false;
this.timer = setInterval(() => this.step(), this.tickMs);
} else {
this.paused = true;
if (this.timer !== null) {
clearInterval(this.timer);
this.timer = null;
}
}
}
/** Full reset to the initial paused-before-start state, then render. Clears the tick interval if running. */
restart(): void {
if (this.timer !== null) {
clearInterval(this.timer);
this.timer = null;
}
this.resetState();
this.updateScoreDom();
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 && !(this.pendingDir.x === -this.dir.x && this.pendingDir.y === -this.dir.y)) {
this.dir = this.pendingDir;
this.pendingDir = null;
}
const newHead: Cell = { x: this.snake[0].x + this.dir.x, y: this.snake[0].y + this.dir.y };
if (this.wouldCollide(newHead, false)) {
this.alive = false;
if (this.timer !== null) {
clearInterval(this.timer);
this.timer = null;
}
this.render();
return;
}
this.snake.unshift(newHead);
if (newHead.x === this.food.x && newHead.y === this.food.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(MIN_TICK_MS, this.tickMs - SPEEDUP_DELTA);
if (this.timer !== null) {
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.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 {
const totalCells = GRID * GRID;
if (this.snake.length >= totalCells) {
this.alive = false;
this.render();
return;
}
let x: number, y: number;
do {
x = Math.floor(Math.random() * GRID);
y = Math.floor(Math.random() * GRID);
} while (this.snake.some(cell => cell.x === x && cell.y === y));
this.food = { x, y };
}
/** 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.fillStyle = COLOR_BG;
this.ctx.fillRect(0, 0, GRID * CELL, GRID * CELL);
this.ctx.fillStyle = COLOR_FOOD;
this.ctx.fillRect(this.food.x * CELL, this.food.y * CELL, CELL, CELL);
this.snake.forEach((cell, index) => {
this.ctx.fillStyle = index === 0 ? COLOR_HEAD : COLOR_BODY;
this.ctx.fillRect(cell.x * CELL, cell.y * CELL, CELL, CELL);
});
this.ctx.fillStyle = COLOR_TEXT;
this.ctx.font = "20px sans-serif";
this.ctx.textAlign = "center";
let text = "";
if (!this.started) {
text = "Press Space to start";
} else if (this.paused) {
text = "Paused";
} else if (!this.alive) {
text = "Game Over — press R to restart";
}
if (text) {
this.ctx.fillText(text, (GRID * CELL) / 2, (GRID * CELL) / 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 {
if (cell.x < 0 || cell.x >= GRID || cell.y < 0 || cell.y >= GRID) return true;
for (let i = 0; i < this.snake.length; i++) {
if (willGrow || i !== this.snake.length - 1) {
if (this.snake[i].x === cell.x && this.snake[i].y === cell.y) return true;
}
}
return false;
}
public 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":
case "W":
game.setPendingDir({ x: 0, y: -1 });
break;
case "ArrowDown":
case "s":
case "S":
game.setPendingDir({ x: 0, y: 1 });
break;
case "ArrowLeft":
case "a":
case "A":
game.setPendingDir({ x: -1, y: 0 });
break;
case "ArrowRight":
case "d":
case "D":
game.setPendingDir({ x: 1, y: 0 });
break;
case " ":
game.togglePause();
break;
case "r":
case "R":
game.restart();
break;
default:
return;
}
e.preventDefault();
});
```