function GravityWellGame() {
	this.game = null;
	this.system = null;

	this.player = null;
	this.ships = [];
	this.bullets = [];
	this.systems = [];
	this.planets = [];

	this.camera = null;
	this.background = null;
	this.farBackground = null;
	this.state = {shipIndex: 1, planetIndex: 1, solarIndex: 1};
	this.shipIndex = 1;
	this.planetIndex = 1;
	this.solarIndex = 1;
	this.settings = {};
	this.settings.enableMouseControl = true;

	this.tickDelay = 60;

	this.init = function(systemObject, canvas) {
		this.game = this;
		this.system = systemObject;

		this.camera = new Camera();
		this.camera.init(canvas);
		this.background = new Scenery(this.camera, 0.1);
		this.farBackground = new Scenery(this.camera, 0.05);
		
		this.systems.push(new SolarSystem(this.game, {x: -40000, y:-40000}));
		this.systems.push(new SolarSystem(this.game, {x: 0, y:-40000}));
		this.systems.push(new SolarSystem(this.game, {x: 40000, y:-40000}));

		this.systems.push(new SolarSystem(this.game, {x: -40000, y:0}));
		this.systems.push(new SolarSystem(this.game, {x: 0, y:0}));
		this.systems.push(new SolarSystem(this.game, {x: 40000, y:0}));

		this.systems.push(new SolarSystem(this.game, {x: -40000, y:40000}));
		this.systems.push(new SolarSystem(this.game, {x: 0, y:40000}));
		this.systems.push(new SolarSystem(this.game, {x: 40000, y:40000}));
		
		

		this.player = new Ship(this.game, new HumanController());
		this.player.id = this.state.shipIndex++;

		for(var index in this.systems) {
			var solar = this.systems[index];
			solar.id = this.state.solarIndex++;
			var solarPlanets = solar.spawnPlanets(this.state);
			var solarShips = solar.spawnShips(this.state);
			this.planets = this.planets.concat(solarPlanets);
			this.ships = this.ships.concat(solarShips);
		}

		var startingSystem = Math.min(Math.max(0, this.systems.length - 1), 4);
		var replaceShip = this.systems[startingSystem].ships[0];
		this.ships.splice(this.ships.indexOf(replaceShip), 1);
		this.ships.push(this.player);
		this.systems[startingSystem].ships[0] = this.player;

		for(var index in this.systems) {
			var solar = this.systems[index];
			solar.init();
		}

		this.ui = new HeadsUpDisplay(this.game, this.camera);
		this.ui.init(this.player, canvas);
	};

	this.tick = function() {
		for(var index in this.systems) {
			var solar = this.systems[index];
			solar.tick();
		}
	};

	this.updateDelta = function(canvas, delta){
		this.tickDelay -= delta;
		if(this.tickDelay <= 0) {
			this.tick();
			this.tickDelay = 60;
		}
		this.update(canvas);

		//this.player.update(delta);

		for(var index in this.ships) {
			var ship = this.ships[index];
			ship.update(delta);
		}

		for(var index in this.systems) {
			var solar = this.systems[index];
			solar.update(delta);
		}

		for(var index in this.bullets) {
			var bullet = this.bullets[index];
			bullet.update(delta);
		}

		this.camera.update(canvas, this.player, delta);
		this.farBackground.update(canvas, delta);
		this.background.update(canvas, delta);

		this.ui.update(delta);
	};

	this.update = function(canvas) {
		//this.player.control();
		
		for(var index in this.ships) {
			var ship = this.ships[index];
			ship.control();
		}

		//bullet-to-ship collision
		for(var index in this.bullets) {
			var bullet = this.bullets[index];
			for(var shipIndex in this.ships) {
				var ship = this.ships[shipIndex];
				if(!ship.isDead) {
					bullet.checkHit(ship);
				}
			}

			//todo: also check planets
		}

		
		for(var index in this.ships) {
			var ship = this.ships[index];
			
			if(ship.isDead) {
				continue;
			}
			//ship-to-ship collision
			for(var shipIndex in this.ships) {
				var otherShip = this.ships[shipIndex];
				if(ship == otherShip) {
					continue;
				}
				ship.checkHit(otherShip);
			}
			//ship-to-planet contact
			for(var systemIndex in this.systems) {
				var otherSystem = this.systems[systemIndex];

				otherSystem.checkCrash(ship);
			}
		}
	};

	this.draw = function(context) {
		this.farBackground.draw(context);
		this.background.draw(context);

		context.save();
		context.translate(this.camera.x, this.camera.y);

		for(var index in this.systems) {
			var solar = this.systems[index];
			solar.draw(context);
		}

		for(var index in this.ships) {
			var ship = this.ships[index];
			ship.draw(context);
		}

		for(var index in this.bullets) {
			var bullet = this.bullets[index];
			bullet.draw(context);
		}

		context.restore();

		this.ui.draw(context);
	};

	this.spawnBullet = function(ship) {
		var newBullet = new Bullet(this.game, ship.id);
		newBullet.fire(ship.position, ship.velocity, ship.targetAngle);
		this.bullets.push(newBullet);
	};

	this.expireBullet = function(bullet) {
		this.bullets.splice(this.bullets.indexOf(bullet), 1);
	}

	this.handleResize = function(canvas) {
		this.camera.handleResize(canvas);
	}

	this.mouseMove = function(canvas, x, y) {
		if(this.settings.enableMouseControl) {
			this.player.controller.mouseSteer(this.player, this.camera, x, y);
		}
	};

	this.mouseDown = function(canvas, button, x, y) {
		if(this.settings.enableMouseControl) {
			switch(button) {
				case 0:
					this.player.shoot();
				break;
				case 2:
					this.player.controller.mouseSteer(this.player, this.camera, x, y);
					this.player.accelerate();
				break;
			}
		}
	};

	this.mouseUp = function(canvas, button, x, y) {
		if(this.settings.enableMouseControl) {
			switch(button) {
				case 2:
					this.player.idle();
				break;
			}
		}
	};

	this.touchStart = function(canvas, x, y) {
		if(this.settings.enableMouseControl) {
			this.player.controller.mouseSteer(this.player, this.camera, x, y);
			this.player.accelerate();
		}
	};

	this.touchMove = function(canvas, x, y) {
		if(this.settings.enableMouseControl) {
			this.player.controller.mouseSteer(this.player, this.camera, x, y);
			this.player.accelerate();
		}
	};

	this.touchEnd = function(canvas, x, y) {
		if(this.settings.enableMouseControl) {
			this.player.idle();
		}
	};

	this.contextMenu = function(canvas, event) {
	};

	this.getNearestPlanet = function(solar, ship) {
		var closestDistance = Number.MAX_SAFE_INTEGER;
		var closestPlanet = null;

		for(var index in solar.planets) {
			var planet = solar.planets[index];
			
			var distance = this.calculateDistanceTo(ship, planet);
			if(distance < closestDistance) {
				closestPlanet = planet;
				closestDistance = distance;
			}

		}
		return closestPlanet;
	}

	this.getNearestSystem = function(game, ship) {
		var closestDistance = Number.MAX_SAFE_INTEGER;
		var closestSystem = null;
		for(var index in game.systems) {
			var solar = game.systems[index];
			
			var distance = this.calculateDistanceTo(ship, solar);
			if(distance < closestDistance) {
				closestSystem = solar;
				closestDistance = distance;
			}
		}
		return closestSystem;
	}

	this.getNearestShip = function(game, ship) {
		var closestDistance = Number.MAX_SAFE_INTEGER;
		var closestShip = null;
		for(var index in game.ships) {
			var other = game.ships[index];
			if(other == ship) {
				continue;
			}
			var distance = this.calculateDistanceTo(ship, other);

			if(distance < closestDistance) {
				closestShip = other;
				closestDistance = distance;
			}
		}

		return closestShip;
	}

	this.calculateDistanceTo = function(ship, other) {
		return Math.sqrt(Math.pow(ship.position.x - other.position.x, 2) + Math.pow(ship.position.y - other.position.y, 2));
	}

	this.calculateAngleTo = function(ship, other) {
		return Math.atan2(ship.position.y - other.position.y , ship.position.x - other.position.x);
	}

	this.calculateAngleToPlanet = function(ship, solar, planet) {
		return Math.atan2((solar.position.y + planet.position.y) - ship.position.y , (solar.position.x + planet.position.x) - ship.position.x);
	}
};