for() loops are so important to understand thoroughly. This tutorial shows you how I create the side of a building by making a window out of a sprite, and then carefully calculating how to squeeze as many on the surface of the building as possible. Download the code below.
Once the windows are installed, you’ll notice that you can mouse over them to turn the inside lamps on — but they’ll go out in a random amount of time.
The blinking blue star is my “controller object” — it builds the building, etc., but doesn’t do anything after that. Note that the building surface itself is just a sprite I’ve dragged onto an independent “Asset” layer — not the “Instances” layer itself. I can do that because the building doesn’t have any code to run. Just the windows (which are placed programmatically on the “Instances” layer, where their code can run.
If you have time, there is a tiny bit of code in the Mouse Enter event that deals with setting an Alarm — a timer — that can be useful.