Feature Reference - The Game Maker's Companion: Game Development - page 368

The lengthdir_x and lengthdir_y functions are used to set the instance to a relative
distance of 100 from the spaceship's position. The variable angle is set up further
below and decides the current angle of position with regard to the spaceship. Line 4
sets a rotation speed; use negative values for clockwise rotation.
3. Open the obj_spaceship object. We use the Create event to create the orbiting stars,
but obviously you may add it in a more appropriate place. Include an Execute Code
action and insert the following lines:
1: {
2: var i;
3: for ( i = 0; i < 360; i += 36)
4: with ( instance_create(0,0,obj_star) ) angle = i;
5: }

This script creates ten evenly distributed stars that each start at a different angle. Line 2
first defines a variable we will use for a for loop. Line 3 sets up the loop from 0 to 360 in
steps of 36 , which amounts to 10 steps (10 stars). Line 4 creates an instance of
obj_star . Note that we do not specify any position here, as this is taken care of in the
star's End Step event using the instance's angle. Using the with statement, we set the
angle variable of the created instance to the value of i (0, 36, 72, 108, and so forth).

4. Because the stars are dependent on the existence of the spaceship, we should destroy

them when the spaceship is destroyed. Add a Destroy event and include a Destroy
Instance action. Select Object , and choose obj_star .

Result: Reference/Result/orbiting_objects.gmk

Patrolling Enemies
Enemies do not always chase the player—often, they're just harmlessly patrolling an area, and the
player's only danger is in touching them. Having enemies walk around a maze with lots of turns
and corners would be a difficult job if it weren't for Game Maker's awesome path mechanisms.

Start with: Reference/Framework/explorer5.gmk

Creating Patrolling Enemies
1.

Create a new object obj_mummy and assign any of the mummy sprites to it. Also create
an object obj_scorpion and assign it any of the scorpion sprites.

Now add a path resource and call it path_mummy1 . To the top right of the path window,
click the Indicate the room to show as background button (it's on the far right at the
top of the window), and select room_test from the drop-down box. Resize the window
if necessary to show the entire room.

2.

3. Uncheck the Closed check box. Make sure that Connection kind is set to Straight

lines .