Game Development Reference
In-Depth Information
}
private function addToScore(val:Number):void {
score += val;
}
Creating functions to fire missiles
The
firePlayerMissile
and
fireMissileAtPlayer
functions are very similar. They actually could
be combined into a single function with some modifications (for example, a
switch:case
statement when a player or enemy fires a missile), but since they have slightly different jobs, we
have kept them separate. They both use the
missileTime
and
missileDelay
properties of the
TileByTileBlitSprite
class to determine if the object trying to fire can actually fire. It does this
by comparing counting frame ticks with the
TileByTileBlitSprite.missileTime
. If the
missileTime
is greater than the
missileDelay
value, a missile will be fired. All missiles are
instances of the
BlitSprite
class.
Once a missile is fired, its direction is set by the direction of the player or enemy firing the missile.
All player missiles travel at 3 pixels per frame tick. This pixel per frame rate can be modified to
come from a variable if you desire a power-up of some sort to make the player's missiles go
faster. The enemy missile speed is governed by the
enemyShotSpeed
for the
lLevel
class instance
The
firePlayerMissile
function is brand new. Copy it completely. The
fireMissileAtPlayer
function already exists (as a stub with a trace).
private function firePlayerMissile():void {
if (player.missileTime++ > player.missileDelay) {
ammo--;
player.missileTime = 0;
//trace("fire a missile");
tempMissile = new BlitSprite(tileSheet, missileTiles, 0);
switch(player.rotation) {
case 0:
tempMissile.dx = 0;
tempMissile.dy = -3;
tempMissile.x = player.x;
tempMissile.y = player.y-10;
break
case 90:
tempMissile.x = player.x+10;
tempMissile.y = player.y;
tempMissile.dx = 3;
tempMissile.dy = 0;
break;
case 180:
tempMissile.x = player.x;
tempMissile.y = player.y+10;
tempMissile.dx = 0;
