Platform Beginnings: An Idea with Legs - The Game Maker's Companion: Game Development - page 20

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Platform Objects
It's difficult to play a platform game without any platforms, so we'll get these made and out of the
way first. We'll start by creating obj_platform , which is probably the most important object in the
game—despite having no events, actions, or even a sprite. This is because it's going to be the
parent object of all other platforms. Hopefully, you'll have come across parent objects before, but
one of the things they allow you to do is group together similar kinds of objects so that they all
behave in the same way. We only create three different platform objects in this example
( obj_rock_begin , obj_rock_middle , obj_rock_end ), but an average platform game would have
many different kinds of platforms, so it's really useful to be able to treat them as a group. Most
significantly, making obj_platform the parent object of these three platforms will mean that we
can test for collisions between Fishpod and obj_platform and this will automatically include
collisions with obj_rock_begin , obj_rock_middle , and obj_rock_end as well. Continue by following
the next set of steps and you'll see how all this comes together when we create the Fishpod
character later on.
Creating the Parent Platform Object
1. Click on the Resources menu and select Create Object (you can also create objects by
right-clicking on the Objects folder in the resource tree, or using the blue ball button
on the toolbar).
2. In the Object Properties form that appears, click on the Name field and enter
obj_platform .
3. Click the OK button on the bottom left of the form to close it. Yes we're done with this object.
Now we will create the rock platform objects, which all use obj_platform as their parent:
Creating the Rock Platform Objects
1. Create a new object resource and enter the Name as obj_rock_middle .
2. Click on the icon at the end of the Sprite field and a list of all the available sprites will
appear. Select the spr_rock_middle sprite.
3. Click on the icon at the end of the Parent field and a list of all the available objects will
appear. Select the obj_platform object.
4. Click the OK button on the bottom left of the form to close it.
5. Repeat steps 1-4 for obj_rock_begin and obj_rock_end , using spr_rock_begin and
spr_rock_end , respectively.
Next we'll do something to help make the process of creating levels a little less fiddly. We
want it to be possible to create rock platforms of any length, but they always need to begin with
an obj_rock_begin and end with an obj_rock_end . That will make positioning and repositioning
platforms in the room editor a bit of a chore—particularly when trying to tweak level designs.
Therefore, we'll automate the process by making every obj_rock_middle automatically create
begin and end platforms either side of it where necessary. That way, we only have to worry about
placing instances of the obj_rock_middle object in the room editor and the object events will
handle the rest for us.