Designing Games with Game Maker - YoYo Games

Under the Run menu you can pause the game, run it step by step and even restart it. Under
the Watch menu you can watch the value of certain expressions. Use Add to type in some
expression whose value is shown in each step of the game. In this way you can see whether
your game is doing things the right way. You can watch many expressions. You can save them
for later use (e.g. after you made a correction to the game). Under the Tools menu you find
items to see even more information. You can see a list of all instances in the game, you can
watch all global variables (well, the most important ones) and the local variables of an
instance (either use the object name or the id of the instance). You can also view messages
which you can send from your code using the function show_debug_message(str). Finally
you can give the game commands and change the speed of the game. If you make
complicated games you should really learn how to use the debug options.
Extension Packages
This functionality is only available in the Pro Edition of Game Maker.
Extension packages extend the possibilities of Game Maker. An extension package can add a
set of actions to Game Maker or it adds a number of additional functions and constants to the
GML language built into Game Maker. When extension packages are available to you, help
about these is placed in the Help menu.
When double clicking on the Extension Packages resource item the following form is shown: