Emanuele Feronato

Talking about Gold Miner game, Actionscript 2, Flash and Game development.

Today I received an email from a reader asking me to make a tutorial of a game like Gold Miner.

It’s a Flash demo of a downloadable game, and I think its gameplay is interesting enough to deserve a tutorial.

The main actor in this game is the hook (in the original game, a claw).

The hook can have three states, that I defined this way:

rotate: that’s when the hook is rotating from left to right at the top of the screen. If the player presses the mouse the state turns to…

shoot: the hook moves in a fixed direction (the one it had when the player pressed the mouse) until it hits a gem or flies off the screen. Then the state turns again to…

rewind: the hook returns, in a straight path, to its initial position and changes the state to rotate, allowing the player to shoot again.

Rewind speed is the same as shoot speed if the hook did not take any boulder, while if the hook has a boulder attached, there will be a slowdown according to boulder size

Let’s see the commented code… remember that the hook is linked as pod while the gem as boulder

// number of boulders in the game
boulders = 20;
for (x=1; x<=boulders; x++) {
	// creating the boulders
	bould = _root.attachMovie("boulder", "boulder_"+_root.getNextHighestDepth(), _root.getNextHighestDepth());
	// placing them in random positions and with random dimensions
	bould._x = Math.floor(Math.random()*400)+50;
	bould._y = Math.floor(Math.random()*200)+150;
	bould._width = Math.floor(Math.random()*30)+20;
	bould._height = bould._width;
	// setting picked attribute as false
	// picked = false => the boulder has not been picked by the hook
	// picked = true => the boulder has been picked
	bould.picked = false;
	// function to be executed at every frame for the boulder
	bould.onEnterFrame = function() {
		// if it's not been picked...
		if (!this.picked) {
			// check if the hook is in shoot mode and touched the boulder
			// you'll see later what do hot_spot_x and hot_spot_y mean
			if (pod_status == "shoot" and this.hitTest(hot_spot_x, hot_spot_y, true)) {
				// set the hook on rewind mode
				pod_status = "rewind";
				// mark this boulder as picked
				this.picked = true;
				// determining the slowdown according to boulder size
				slowdown = Math.floor(this._width/5);
			}
		}
		else {
			// the boulder has been picked, so move it as the hook moves
			this._x = hot_spot_x;
			this._y = hot_spot_y;
			// if the hook status changed to rotate
			// (this means: if the hook took a boulder and pulled it out to surface...
			if (pod_status == "rotate") {
				// remove the boulder
				this.removeMovieClip();
			}
		}
	};
}
// placing the hook on stage
_root.attachMovie("pod","pod",_root.getNextHighestDepth(),{_x:250});
// creating an empty movie clip to draw the rope
_root.createEmptyMovieClip("rod",_root.getNextHighestDepth());
// this is the rotation direction and speed
rotation_dir = 2;
// hook initial status
pod_status = "rotate";
// slowdown malus
slowdown = 0;
// function the hook will execute at every frame
pod.onEnterFrame = function() {
	// getting pod status
	switch (pod_status) {
		case "rotate" :
			// if the status is rotate, just rotate the hook according to rotation_dir
			this._rotation += rotation_dir;
			if (this._rotation == 80 or this._rotation == -80) {
				// invert rotation_dir if the hook reaches its minimum (or maximum) rotation allowed
				rotation_dir *= -1;
			}
			break;
		case "shoot" :
			// the hook has ben shoot
			// (re)set slowdown malus to zero
			slowdown = 0;
			// moving the hook using trigonometry
			this._x += 10*Math.cos(dir);
			this._y += 10*Math.sin(dir);
			// determining the hot spot of the hook
			// the hot spot is the lowest corner of the hook (that acts like an harpoon in this case)
			hot_spot_x = this._x+40*Math.cos(dir);
			hot_spot_y = this._y+40*Math.sin(dir);
			// if the hot spot goes off the stage
			if (hot_spot_y>400 or hot_spot_x<0 or hot_spot_x>500) {
				// then rewind the hook
				pod_status = "rewind";
			}
			// draw a line from the hook starting position to its actual position 
			// this will simulate the rope
			rod.clear();
			rod.lineStyle(1,0x000000);
			rod.moveTo(250,0);
			rod.lineTo(this._x,this._y);
			break;
		case "rewind" :
			// rewinding the hook...
			// it may seem a nonsense determining the hot spot now, but I need id
			// to move the boulder (if I have any boulder attached to the hook)
			hot_spot_x = this._x+40*Math.cos(dir);
			hot_spot_y = this._y+40*Math.sin(dir);
			// moving the hook with slowdown malus (if any)
			this._x -= (10-slowdown)*Math.cos(dir);
			this._y -= (10-slowdown)*Math.sin(dir);
			// if the hook returns in its initial position...
			if (this._y<0) {
				// then reset its position and set its status to rotate
				this._y = 0;
				this._x = 250;
				pod_status = "rotate";
			}
			// drawing a line as seen in shoot status
			rod.clear();
			rod.lineStyle(1,0x000000);
			rod.moveTo(250,0);
			rod.lineTo(this._x,this._y);
			break;
	}
};
// when the mouse is clicked...
_root.onMouseDown = function() {
	// if the status is rotate...
	if (pod_status == "rotate") {
		// save hook heading and convert it to radians
		dir = (pod._rotation+90)*0.0174532925;
		// set pod status to shoot
		pod_status = "shoot";
	}
};

And this is the result

As you can see, the basics have been reproduced.

Download the source code.