Flash ball vs ball game concept

//functions
function findAnAngle(xthing, ything) {
	//very basic angle finder..returns value in degrees  
	term = Math.PI/180;
	//degree->radian
	if (xthing<0) {
		t = 180+Math.atan(ything/xthing)/term;
	} else if (xthing>0 && ything>=0) {
		t = Math.atan(ything/xthing)/term;
	} else if (xthing>0 && ything<0) {
		t = 360+Math.atan(ything/xthing)/term;
	} else if (xthing == 0 && ything == 0) {
		t = 0;
	} else if (xthing == 0 && ything>=0) {
		t = 90;
	} else {
		t = 270;
	}
	return t;
}
function doCollision(ball, ball2) {
	dx = ball._x-ball2._x;
	dy = ball._y-ball2._y;
	phi = Math.atan(dy/dx);
	//find the collision angle
	term = Math.PI/180;
	//degree->radian
	//find out the magnitude of the velocities of the two balls
	v1i = Math.sqrt(ball.vx*ball.vx+ball.vy*ball.vy);
	v2i = Math.sqrt(ball2.vx*ball2.vx+ball2.vy*ball2.vy);
	//find out the angle of the velocity vector
	ang1 = findAnAngle(ball.vx, ball.vy)*term;
	ang2 = findAnAngle(ball2.vx, ball2.vy)*term;
	//find the velocities in the new coordinate system
	v1xr = v1i*Math.cos(ang1-phi);
	v1yr = v1i*Math.sin(ang1-phi);
	v2xr = v2i*Math.cos(ang2-phi);
	v2yr = v2i*Math.sin(ang2-phi);
	//find the final velocities in the normal reference frame
	//the x velocities will obey the rules for a 1-D collision
	v1fxr = ((ball.mass-ball2.mass)*v1xr+(ball2.mass+ball2.mass)*v2xr)/(ball.mass+ball2.mass);
	v2fxr = ((ball.mass+ball.mass)*v1xr+(ball2.mass-ball.mass)*v2xr)/(ball.mass+ball2.mass);
	//the y velocities will not be changed
	v1fyr = v1yr;
	v2fyr = v2yr;
	//convert back to the standard x,y coordinates
	_root.ball.vx = Math.cos(phi)*v1fxr+Math.cos(phi+Math.PI/2)*v1fyr;
	_root.ball.vy = Math.sin(phi)*v1fxr+Math.sin(phi+Math.PI/2)*v1fyr;
	_root.ball2.vx = Math.cos(phi)*v2fxr+Math.cos(phi+Math.PI/2)*v2fyr;
	_root.ball2.vy = Math.sin(phi)*v2fxr+Math.sin(phi+Math.PI/2)*v2fyr;
}
//move ball
MovieClip.prototype.move = function() {
	this.onEnterFrame = function() {
		//check for collision with walls, done pretty quick
		//the balls might get stuck in the walls if they move too fast
		if ((ball._x<45) or (ball._x>579)) {
			bdead = true;
		}
		if ((ball._y<40) or (ball._y>424)) {
			bdead = true;
		}
		if ((ball2._x<45) or (ball2._x>579)) {
			b2dead = true;
		}
		if ((ball2._y<40) or (ball2._y>424)) {
			b2dead = true;
		}
		//move 
		this._x += this.vx;
		this._y += this.vy;
	};
};
_root.onLoad = function() {
	ball.mass = 20;
	ball.vx = 0;
	ball.vy = 0;
	ball.move();
	ball2.mass = 20;
	ball2.vx = 0;
	ball2.vy = 0;
	ball2.move();
	coll = 0;
	friction = 0.1;
	gws = 0;
	ba = 0.8;
	nmea = 0.8;
	radius = 15;
	bdead = false;
	b2dead = false;
};
_root.onEnterFrame = function() {
	//we check for collision using the distance between the two centre points of the balls
	//if that distance is smaller than two times the radius of the balls we have collision
	//the radius is hardcoded
	distance_x = Math.abs(ball._x-ball2._x);
	distance_y = Math.abs(ball._y-ball2._y);
	distance = Math.sqrt(distance_x*distance_x+distance_y*distance_y);
	//make sure the balls don't get stuck into eachother
	if (distance<=30 && coll == 0) {
		coll = 1;
		doCollision(ball, ball2);
	} else if (distance>30) {
		coll = 0;
	}
	//Player One controls 
	if (Key.isDown(Key.RIGHT) && ball.vx<10) {
		ball.vx += ba;
	}
	if (Key.isDown(Key.LEFT) && ball.vx>-10) {
		ball.vx -= ba;
	}
	if (Key.isDown(Key.UP) && ball.vy>-10) {
		ball.vy -= ba;
	}
	if (Key.isDown(Key.DOWN) && ball.vy<10) {
		ball.vy += ba;
	}
	//Friction 
	if (ball.vx>0) {
		ball.vx -= friction;
	} else if (ball.vx<0) {
		ball.vx += friction;
	}
	if (ball.vy>0) {
		ball.vy -= friction;
	} else if (ball.vy<0) {
		ball.vy += friction;
	}
	if (ball2.vx>0) {
		ball2.vx -= friction;
	} else if (ball2.vx<0) {
		ball2.vx += friction;
	}
	if (ball2.vy>0) {
		ball2.vy -= friction;
	} else if (ball2.vy<0) {
		ball2.vy += friction;
	}
	//Gravity well! 
	if (ball._x>320) {
		ball.vx -= gws;
	} else if (ball._x<320) {
		ball.vx += gws;
	}
	if (ball._y>240) {
		ball.vy -= gws;
	} else if (ball._y<240) {
		ball.vy += gws;
	}
	if (ball2._x>320) {
		ball2.vx -= gws;
	} else if (ball2._x<320) {
		ball2.vx += gws;
	}
	if (ball2._y>240) {
		ball2.vy -= gws;
	} else if (ball2._y<240) {
		ball2.vy += gws;
	}
	//Tracking AI 
	if ((ball2._x<ball._x) && ball2.vx<10) {
		ball2.vx += nmea;
	}
	if ((ball2._x>ball._x) && ball2.vx>-10) {
		ball2.vx -= nmea;
	}
	if ((ball2._y>ball._y) && ball2.vy>-10) {
		ball2.vy -= nmea;
	}
	if ((ball2._y<ball._y) && ball2.vy<10) {
		ball2.vy += nmea;
	}
	//Death 
	if (bdead == true) {
		ball.vx = ball.vx/3;
		ball.vy = ball.vy/3;
		ball2.vx = 0;
		ball2.vy = 0;
		if (ball._xscale>0) {
			ball._xscale -= 2;
			ball._yscale -= 2;
			ball._alpha -= 1;
		}
	}
	if (b2dead == true) {
		ball.vx = 0;
		ball.vy = 0;
		ball2.vx = ball2.vx/3;
		ball2.vy = ball2.vy/3;
		if (ball2._xscale>0) {
			ball2._xscale -= 2;
			ball2._yscale -= 2;
			ball2._alpha -= 1;
		}
	}
};
_root.onMouseDown = function() {
	ball.vx = 0;
	ball.vy = 0;
	ball2.vx = 0;
	ball2.vy = 0;
	ball._x = 245;
	ball._y = 170;
	ball2._x = 165;
	ball2._y = 222;
	bdead = false;
	b2dead = false;
	ball._xscale = 100;
	ball._yscale = 100;
	ball._alpha = 100;
	ball2._xscale = 100;
	ball2._yscale = 100;
	ball2._alpha = 100;
};