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AlienEntity.snap
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AlienEntity.snap
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/**
* An entity which represents one of our space invader aliens.
*/
class AlienEntity extends Entity {
/** The speed at which the alient moves horizontally */
var moveSpeed = 75.0;
/** The game in which the entity exists */
var game;
/**
* Create a new alien entity
*
* @param game The game in which this entity is being created
* @param ref The sprite which should be displayed for this alien
* @param x The intial x location of this alien
* @param y The intial y location of this alient
*/
new(game, ref, x, y) : super(ref,x,y){
this.game = game;
this.dx = -moveSpeed;
}
/**
* Request that this alien moved based on time elapsed
*
* @param delta The time that has elapsed since last move
*/
move(delta) {
// if we have reached the left hand side of the screen and
// are moving left then request a logic update
if (dx < 0 && x < 10) {
game.updateLogic();
}
// and vice vesa, if we have reached the right hand side of
// the screen and are moving right, request a logic update
if (dx > 0 && x > 750) {
game.updateLogic();
}
// proceed with normal move
super.move(delta);
}
/**
* Update the game logic related to aliens
*/
doLogic() {
// swap over horizontal movement and move down the
// screen a bit
dx = -dx;
y += 10;
// if we've reached the bottom of the screen then the player
// dies
if (y > 570) {
game.notifyDeath();
}
}
/**
* Notification that this alien has collided with another entity
*
* @param other The other entity
*/
collidedWith(other) {
// collisions with aliens are handled elsewhere
}
}