Designing Games with Game Maker - YoYo Games

e the way you left it the last time. Checking the box labeled Persistent will do exactly that.
The room status will be remembered and when you return to it later, it will be exactly the
same as you left it. Only when you restart the game will the room be reset. Actually, there is
one exception to this. If you marked certain objects as being persistent, instances of this
object will not stay in the room but move to the next room.
Secondly, there is a button labeled Creation code. Here you can type in a piece of code in
GML (see later) that is executed when the room is created. This is useful to fill in certain
variables for the room, create certain instances, etc. It is important to understand what
exactly happens when you move to a particular room in the game.
• First, in the current room (if any) all instances get a room-end event. Next the non-
persistent instances are removed (no destroy event is generated!).
• Next, for the new room the persistent instances from the previous room are added.
• All new instances are created and their creation events are executed (if the room is
not persistent or has not been visited before).
• When this is the first room, for all instances the game-start event is generated.
• Now the room creation code is executed.
• Finally, all instances get a room-start event.
So, for example, the room-start events can use variables set by the creation code for the
room and in the creation code you can refer to the instances (both new ones and persistent
ones) in the room.
There is one further option. In the pop-up menu when you right click on an instance with the
key you can now indicate some creation code for the specific instance. This code is
executed when the room is started, just before the creation event of the instance is executed.
This is very useful to e.g. set certain parameters that are specific to the instance.
Adding tiles
You can also create so-called tiled background. The reason for this is as follows: In many
games you will want to have nice looking backgrounds. For example, in a maze game, the
walls of the maze should nicely match up, and in platform games you like to see beautifully
drawn platforms, trees, etc. You can do this in Game Maker by defining many different objects
and composing your rooms from these objects. The problem though is that this takes a lot of
work, uses large amounts of resources, and makes the games run slowly because of the many