It lacks more in engine power than it is capable of doing, even if it's a kid-friendly entry into the programming world. You're probably better off straight-up learning to program in for example C++, Python, Java, Basic, Pascal, Lua... you name it, really.
Game Maker Language, however, is C-based or at least very similar to it - so I guess it's a good step up to getting started.
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My final advice, I think, is that although you can create pretty neat games that work alright to well, Game Maker has severely dysfunctional limits to what it can do for you and you should probably look for alternatives pretty soon after you've started meddling around in it. It's nice, but it's not excellent.
Also the Support service has gone to shit, but that's another matter.



