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game.js
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game.js
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var sprites = {
ship: { sx: 2, sy: 0, w: 37, h: 42, frames: 1 },
missile: { sx: 0, sy: 30, w: 2, h: 10, frames: 1 },
enemy_purple: { sx: 37, sy: 0, w: 42, h: 43, frames: 1 },
enemy_bee: { sx: 79, sy: 0, w: 37, h: 43, frames: 1 },
enemy_ship: { sx: 116, sy: 0, w: 42, h: 43, frames: 1 },
enemy_circle: { sx: 158, sy: 0, w: 32, h: 33, frames: 1 },
explosion: { sx: 0, sy: 64, w: 64, h: 64, frames: 12 },
enemy_missile: { sx: 9, sy: 42, w: 3, h: 20, frame: 1, }
};
var enemies = {
straight: { x: 0, y: -50, sprite: 'enemy_ship', health: 10,
E: 100 },
ltr: { x: 0, y: -100, sprite: 'enemy_purple', health: 10,
B: 75, C: 1, E: 100, missiles: 2 },
circle: { x: 250, y: -50, sprite: 'enemy_circle', health: 10,
A: 0, B: -100, C: 1, E: 20, F: 100, G: 1, H: Math.PI/2 },
wiggle: { x: 100, y: -50, sprite: 'enemy_bee', health: 20,
B: 50, C: 4, E: 100, firePercentage: 0.001, missiles: 2},
step: { x: 0, y: -50, sprite: 'enemy_circle', health: 10,
B: 150, C: 1.2, E: 75 }
};
var OBJECT_PLAYER = 1,
OBJECT_PLAYER_PROJECTILE = 2,
OBJECT_ENEMY = 4,
OBJECT_ENEMY_PROJECTILE = 8,
OBJECT_POWERUP = 16;
var startGame = function() {
var ua = navigator.userAgent.toLowerCase();
// Only 1 row of stars
if(ua.match(/android/)) {
Game.setBoard(0,new Starfield(50,0.6,100,true));
} else {
Game.setBoard(0,new Starfield(20,0.4,100,true));
Game.setBoard(1,new Starfield(50,0.6,100));
Game.setBoard(2,new Starfield(100,1.0,50));
}
Game.setBoard(3,new TitleScreen("Alien Invasion",
"Press fire to start playing",
playGame));
};
var level1 = [
// Start, End, Gap, Type, Override
[ 0, 4000, 500, 'step' ],
[ 6000, 13000, 800, 'ltr' ],
[ 10000, 16000, 400, 'circle' ],
[ 17800, 20000, 500, 'straight', { x: 50 } ],
[ 18200, 20000, 500, 'straight', { x: 90 } ],
[ 18200, 20000, 500, 'straight', { x: 10 } ],
[ 22000, 25000, 400, 'wiggle', { x: 150 }],
[ 22000, 25000, 400, 'wiggle', { x: 100 }]
];
var playGame = function() {
var board = new GameBoard();
board.add(new PlayerShip());
board.add(new Level(level1,winGame));
Game.setBoard(3,board);
Game.setBoard(5,new GamePoints(0));
};
var redirect = function()
{
setTimeout(function() {
window.location.href = "https://iecsemanipal.com/";
}, 6000);
}
var winGame = function() {
Game.setBoard(3,new EndGameScreen("You win!",
" ",
redirect));
setTimeout(function() {
window.location.href = "https://iecsemanipal.com/";
}, 6000);
};
var loseGame = function() {
Game.setBoard(3,new EndGameScreen("Better luck next time!",
" ",
redirect));
setTimeout(function() {
window.location.href = "https://iecsemanipal.com/";
}, 6000);
};
var Starfield = function(speed,opacity,numStars,clear) {
// Set up the offscreen canvas
var stars = document.createElement("canvas");
stars.width = Game.width;
stars.height = Game.height;
var starCtx = stars.getContext("2d");
var offset = 0;
// If the clear option is set,
// make the background black instead of transparent
if(clear) {
starCtx.fillStyle = "#000";
starCtx.fillRect(0,0,stars.width,stars.height);
}
// Now draw a bunch of random 2 pixel
// rectangles onto the offscreen canvas
starCtx.fillStyle = "#FFF";
starCtx.globalAlpha = opacity;
for(var i=0;i<numStars;i++) {
starCtx.fillRect(Math.floor(Math.random()*stars.width),
Math.floor(Math.random()*stars.height),
2,
2);
}
// This method is called every frame
// to draw the starfield onto the canvas
this.draw = function(ctx) {
var intOffset = Math.floor(offset);
var remaining = stars.height - intOffset;
// Draw the top half of the starfield
if(intOffset > 0) {
ctx.drawImage(stars,
0, remaining,
stars.width, intOffset,
0, 0,
stars.width, intOffset);
}
// Draw the bottom half of the starfield
if(remaining > 0) {
ctx.drawImage(stars,
0, 0,
stars.width, remaining,
0, intOffset,
stars.width, remaining);
}
};
// This method is called to update
// the starfield
this.step = function(dt) {
offset += dt * speed;
offset = offset % stars.height;
};
};
var PlayerShip = function() {
this.setup('ship', { vx: 0, reloadTime: 0.25, maxVel: 200 });
this.reload = this.reloadTime;
this.x = Game.width/2 - this.w / 2;
this.y = Game.height - Game.playerOffset - this.h;
this.step = function(dt) {
if(Game.keys['left']) { this.vx = -this.maxVel; }
else if(Game.keys['right']) { this.vx = this.maxVel; }
else { this.vx = 0; }
this.x += this.vx * dt;
if(this.x < 0) { this.x = 0; }
else if(this.x > Game.width - this.w) {
this.x = Game.width - this.w;
}
this.reload-=dt;
if(Game.keys['fire'] && this.reload < 0) {
Game.keys['fire'] = false;
this.reload = this.reloadTime;
this.board.add(new PlayerMissile(this.x,this.y+this.h/2));
this.board.add(new PlayerMissile(this.x+this.w,this.y+this.h/2));
}
};
};
PlayerShip.prototype = new Sprite();
PlayerShip.prototype.type = OBJECT_PLAYER;
PlayerShip.prototype.hit = function(damage) {
if(this.board.remove(this)) {
loseGame();
}
};
var PlayerMissile = function(x,y) {
this.setup('missile',{ vy: -700, damage: 10 });
this.x = x - this.w/2;
this.y = y - this.h;
};
PlayerMissile.prototype = new Sprite();
PlayerMissile.prototype.type = OBJECT_PLAYER_PROJECTILE;
PlayerMissile.prototype.step = function(dt) {
this.y += this.vy * dt;
var collision = this.board.collide(this,OBJECT_ENEMY);
if(collision) {
collision.hit(this.damage);
this.board.remove(this);
} else if(this.y < -this.h) {
this.board.remove(this);
}
};
var Enemy = function(blueprint,override) {
this.merge(this.baseParameters);
this.setup(blueprint.sprite,blueprint);
this.merge(override);
};
Enemy.prototype = new Sprite();
Enemy.prototype.type = OBJECT_ENEMY;
Enemy.prototype.baseParameters = { A: 0, B: 0, C: 0, D: 0,
E: 0, F: 0, G: 0, H: 0,
t: 0, reloadTime: 0.75,
reload: 0 };
Enemy.prototype.step = function(dt) {
this.t += dt;
this.vx = this.A + this.B * Math.sin(this.C * this.t + this.D);
this.vy = this.E + this.F * Math.sin(this.G * this.t + this.H);
this.x += this.vx * dt;
this.y += this.vy * dt;
var collision = this.board.collide(this,OBJECT_PLAYER);
if(collision) {
collision.hit(this.damage);
this.board.remove(this);
}
if(Math.random() < 0.01 && this.reload <= 0) {
this.reload = this.reloadTime;
if(this.missiles == 2) {
this.board.add(new EnemyMissile(this.x+this.w-2,this.y+this.h));
this.board.add(new EnemyMissile(this.x+2,this.y+this.h));
} else {
this.board.add(new EnemyMissile(this.x+this.w/2,this.y+this.h));
}
}
this.reload-=dt;
if(this.y > Game.height ||
this.x < -this.w ||
this.x > Game.width) {
this.board.remove(this);
}
};
Enemy.prototype.hit = function(damage) {
this.health -= damage;
if(this.health <=0) {
if(this.board.remove(this)) {
Game.points += this.points || 100;
this.board.add(new Explosion(this.x + this.w/2,
this.y + this.h/2));
}
}
};
var EnemyMissile = function(x,y) {
this.setup('enemy_missile',{ vy: 200, damage: 10 });
this.x = x - this.w/2;
this.y = y;
};
EnemyMissile.prototype = new Sprite();
EnemyMissile.prototype.type = OBJECT_ENEMY_PROJECTILE;
EnemyMissile.prototype.step = function(dt) {
this.y += this.vy * dt;
var collision = this.board.collide(this,OBJECT_PLAYER)
if(collision) {
collision.hit(this.damage);
this.board.remove(this);
} else if(this.y > Game.height) {
this.board.remove(this);
}
};
var Explosion = function(centerX,centerY) {
this.setup('explosion', { frame: 0 });
this.x = centerX - this.w/2;
this.y = centerY - this.h/2;
};
Explosion.prototype = new Sprite();
Explosion.prototype.step = function(dt) {
this.frame++;
if(this.frame >= 12) {
this.board.remove(this);
}
};
window.addEventListener("load", function() {
Game.initialize("game",sprites,startGame);
});