game-platform/game.js

import * as lib from "./lib.js"

const playerSprite = await lib.texture.loadImage("assets/player.png", 64, 64);
const bulletSprite = await lib.texture.loadImage("assets/bullet1.png", 24, 24);
const enemySprite = await  lib.texture.loadImage("assets/enemy1.png", 48, 48);

const explosionSprites = [
    await lib.texture.loadImage(`assets/explosion1.png`, 64, 64),
    await lib.texture.loadImage(`assets/explosion2.png`, 64, 64),
    await lib.texture.loadImage(`assets/explosion3.png`, 64, 64),
    await lib.texture.loadImage(`assets/explosion4.png`, 64, 64),
];

const enemyBullet = bulletSprite.copy();

playerSprite.adjustColor(1, 0.5, 0);
bulletSprite.rotate(Math.PI);
enemySprite.adjustColor(0.2, 0.2, 1);
enemyBullet.adjustColor(0, 1, 0);

for (const texture of explosionSprites) {
    texture.adjustColor(1, 0.75, 0);
}

const playerSpeed = 300;
const bulletSpeed = 400;

let playerX = 0;

let bullets = [];
const bulletCoolDown = 0.5;
let bulletCooldownTimer = bulletCoolDown;

let enemies = [];

let explosions = [];
const explosionDuration = 0.5;

function loop() {
    tick();
    render();
}

function tick() {
    bulletCooldownTimer += lib.frameDeltaT;

    if (enemies.length === 0) {
        spawnEnemies();
    }

    updatePlayerMovement();
    updateBulletMovement();
    handleBulletCollisions();
    updateExplosions();
}

function updatePlayerMovement() {
    const goLeft = lib.isPressed("ArrowLeft");
    const goRight = lib.isPressed("ArrowRight");

    if (goLeft && !goRight) {
        playerX -= playerSpeed * lib.frameDeltaT;
        if (playerX < 0) {
            playerX = 0;
        }
    } else if (goRight && !goLeft) {
        playerX += playerSpeed * lib.frameDeltaT;
        if (playerX >= lib.canvas.width - playerSprite.width) {
            playerX = lib.canvas.width - playerSprite.width;
        }
    }
}

function updateBulletMovement() {
    for (const bullet of bullets) {
        bullet.y -= bulletSpeed * lib.frameDeltaT;
    }
}

function handleBulletCollisions() {
    let deadEnemies = []
    let deadBullets = []
    for (let enemyIdx = 0; enemyIdx < enemies.length; ++enemyIdx) {

        const enemy = enemies[enemyIdx];

        for (let bulletIdx = 0; bulletIdx < bullets.length; ++bulletIdx) {
            const bullet = bullets[bulletIdx];

            if (bullet.x < enemy.x + 48 && bullet.x + 24 >= enemy.x
                && bullet.y < enemy.y + 48 && bullet.y + 24 >= enemy.y) {
                deadBullets.push(bulletIdx);
                deadEnemies.push(enemyIdx);
                explosions.push({ x: enemy.x + 24, y: enemy.y + 24, time: 0 });
            }

        }
    }
    for (const i of deadEnemies.toReversed()) {
        enemies.splice(i, 1)
    }
    for (const i of deadBullets.toReversed()) {
        bullets.splice(i, 1)
    }
}

function updateExplosions() {
    let deadExplosions = []
    for (let i = 0; i < explosions.length; ++i) {
        const explosion = explosions[i];
        explosion.time += lib.frameDeltaT;
        if (explosion.time > explosionDuration) {
            deadExplosions.push(i);
        }
    }
    for (const i of deadExplosions.toReversed()) {
        explosions.splice(i, 1)
    }
}

function spawnEnemies() {
    for (let y = 0; y < 2; ++y) {
        for (let x = 0; x < 5; ++x) {
            enemies.push({ x: 10 + 100 * x, y: y * 80 });
        }
    }
}

function render() {
    const cx = lib.canvas;

    cx.clear("black");

    cx.putTexture(playerSprite, playerX, 300);

    for (const bullet of bullets) {
        cx.putTexture(bulletSprite, bullet.x, bullet.y);
    }

    for (const enemy of enemies) {
        cx.putTexture(enemySprite, enemy.x, enemy.y);
    }

    for (const explosion of explosions) {
        const idx = Math.floor(explosionSprites.length * (explosion.time / explosionDuration));
        const texture = explosionSprites[idx];
        cx.putTexture(texture, explosion.x - 32, explosion.y - 32);
    }
}

lib.onPress(" ", () => {
    if (bulletCooldownTimer < bulletCoolDown)
        return;
    bullets.push({ x: playerX + 20, y: 300 });
    bulletCooldownTimer = 0;
})

lib.startGame(loop);