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gameengine.js
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gameengine.js
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// This game shell was happily modified from Googler Seth Ladd's "Bad Aliens" game and his Google IO talk in 2011
class GameEngine {
constructor() {
this.entities = [];
this.ctx = null;
this.surfaceWidth = null;
this.surfaceHeight = null;
this.tick = 0;
};
init(ctx) { // called after page has loaded
this.ctx = ctx;
this.surfaceWidth = this.ctx.canvas.width;
this.surfaceHeight = this.ctx.canvas.height;
this.startInput();
this.timer = new Timer();
};
start() {
var that = this;
(function gameLoop() {
that.loop();
requestAnimFrame(gameLoop, that.ctx.canvas);
})();
};
startInput() {
};
addEntity(entity) {
this.entities.push(entity);
};
draw() {
this.ctx.clearRect(0, 0, this.ctx.canvas.width, this.ctx.canvas.height);
this.ctx.save();
this.ctx.translate(400, 400);
var zoom = document.getElementById("zoom").value;
this.ctx.scale(zoom, zoom);
for (var i = 0; i < this.entities.length; i++) {
this.entities[i].draw(this.ctx);
}
this.ctx.restore();
this.ctx.font = "10px Arial";
this.ctx.fillStyle = "White";
this.ctx.fillText(this.tick++, 5, 15);
};
update() {
var entitiesCount = this.entities.length;
for (var i = 0; i < entitiesCount; i++) {
var entity = this.entities[i];
if (!entity.removeFromWorld) {
entity.move();
}
}
for (var i = 0; i < entitiesCount; i++) {
var entity = this.entities[i];
if (!entity.removeFromWorld) {
entity.update();
}
}
for (var i = this.entities.length - 1; i >= 0; --i) {
if (this.entities[i].removeFromWorld) {
this.entities.splice(i, 1);
}
}
};
loop() {
this.clockTick = this.timer.tick();
this.update();
this.draw();
};
};