Game Development Reference
In-Depth Information
The preceding code will move enemies at the same speed as the background is moved,
and will move the enemy to a somewhat random position in front of the screen once
it goes off screen. This way we will always use only a certain amount of enemies and
won't create any new ones. Re-using things is a good practice, since it saves us memory
and processor time. Next, we need to add some constants that handle the number of
enemies that spawn and power-ups that can spawn.
We will add these to
Common.h
:
const static NSInteger maximumEnemies = 3;
const static NSInteger maximumPowerups = 1;
Now back in
ERGMyScene.m
, we will create new enemies and power-ups in the
initWithSize:
method:
for (int i = 0; i < maximumEnemies; i++) {
[self addChild:[self spawnEnemy]];
}
for (int i = 0; i < maximumPowerups; i++) {
[self addChild:[self spawnPowerup]];
}
Now it's time to change the appearance of enemies. Create a new particle effects file
for them and name it as
enemy.sks
. You can configure them the way you like, but I
used the following properties for enemies:
•
Particles:
500
•
Lifetime:
0.05
•
Position and range:
zero
•
Angle:
0
with
360
range
•
Speed:
400
•
Acceleration: Zero on both the axes
•
Scale:
0.1
with
0.1
range and
1
speed
•
Rotation: At zero and yellow color
And the following properties for power-ups:
•
Particles:
400
•
Lifetime:
1
•
Position range:
X
at
20
and
Y
at
0
•
Angle:
90
with
0
range
