Designing Games with Game Maker - YoYo Games

You can add comment to your programs. Everything on a line after // is not read. You can also
make a multi-line comment by placing the text between / * and */. (Colorcoding might not
work correctly here! Press F12 to re- colorcode the text if an error occurs.)
Functions and variables in GML
GML contains a large number of built-in functions and variables. With these you can control
any part of the game. For all actions there are corresponding functions so you actually don't
need to use any actions if you prefer using code. But there are many more functions and
variables that control aspects of the game that cannot be used with actions only. So if you
want to make advanced games you are strongly advised to read through the following
chapters to get an overview of all that is possible. Please note that these variables and
functions can also be used when providing values for actions. So even if you don't plan on
using code or writing scripts, you will still benefit from this information.
The following convention is used below. Variable names marked with a * are read-only, that
is, their value cannot be changed. Variable names with [0..n] after them are arrays. The range
of possible indices is given.
Computing things
Game Maker contains a large number of functions to compute certain things. Here is a
complete list.
Constants
The following mathematical constants exist:
true Equal to 1.
false Equal to 0.
pi Equal to 3.1415...
Real-valued functions
The following functions exist that deal with real numbers.
random(x) Returns a random real number between 0 and x. The number is
always smaller than x.