Elysian Shadows

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To me, it depends on what is your goal. If you want to learn how things work in game development, Game Maker can't help you. It can give you an idea of how things are structured on a game engine, if you have no clue, but nothing beyond that. For this, you will have to delve into a real programming language and create a game from scratch.

But if your goal is just to make a game, Game Maker surely is the best choice. If you don't care how things are implemented, just use it. I see no difference (when you abstract away the proportions, of course) between using Game Maker or some professional engine like Unity. You just have to be aware of the limitations of the platform.

GameMaker doesn't work well to further your programming skill, and whether or not that's a problem is up to you, obviously. However, unless the engine has changed since I played with it, building an RPG in it would be reeeeally inefficient and irritating (and that's coming from someone who regularly writes Java and AS3 along with C/++).

There are great games built with GameMaker, but it isn't very robust and the development process is completely different than most engines'. You often have to jump through hoops to make something that would frankly be simple to actually program work in it. It may have changed, but last time I looked, tiles in GameMaker weren't indices but fully separate entities(!) under the hood, so an RPG may cause some extra pain.

Spelunky is a good GameMaker game, but if you ever take a peek at its source code you'll be amazed how much the fact the creator chose GameMaker bloated and overcomplicated most things.

Honestly, if you're wanting to use a pre-built engine to make a maze RPG game, there are tons of better options, many of them free and varying in how much they'll help you grow as a programmer. I'll start with some free Flash ones:

Stencyl (no skill required, completely guided like GameMaker but simpler to add shit to, is not super robust. Pixel based.)
Flixel (programming library, free and easy to learn, has some convenient things built in, entity system isn't the best ever but for most oldschool games it isn't a problem. Pixel based.)
Flashpunk (I have zero knowledge here, popular alternative library to Flixel.)
Citrus (my favourite Flash-based game engine. Super powerful and able to be efficient [for Flash] if you use it well, very flexible, but likely overpowered for an oldschool RPG.)

Now, if you're wanting to further your study toward productive ends besides game development and web development isn't your thing, obviously you might not want to spend a lot of time on AS3, especially if you aren't familiar with it, but I thought I'd still throw out some options in case you're interested.

Somewhat better, there are lots of free Java libraries as well.

Slick2D (a dev library that greatly simplifies the development process, can be used for efficient games, has built in and easily-extended functionality for loading Tiled maps.)
LWJGL (Light Weight Java Game Library, provides all the basic APIs you need to make a game engine in Java, including OpenGL rendering, input, and other goodies.)

Something really good for RPG games is RPG Maker XP, whose Ruby-scripted engine can be nearly fully customized to fit your needs. I dunno how the other versions of RPG Maker compare, though, and I've seen small games have huge file sizes before for no apparent reason.

Of course, if you want something overpowered as fuck, you can always get familiar with Unity3D, but for a 2D RPG maze game it's obviously insane overkill.

Sorry for the huge post, just wanted to throw out some if-not-better-then-more-educational-than-GameMaker options for you. Of course, if you prefer GameMaker, there's nothing wrong with using it unless it isn't suited to your game, but personally I found it to be a massive pain in the ass to deal with.

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I pretty much agree with what has already been stated...

In the arrogance of my youth (lol), I definitely was guilty of turning up my nose at Game Maker "developers." In reality, it truly does depend on what your goal is.

If you are just looking to pump out a quick game and aren't serious about bettering your programming career or learning the intricacies of the field of computer science, there really is nothing wrong with Game Maker...

However, if you are looking to take your game development to the next level, and you plan on using Game Maker more than as an introductory tool to get your foot in the door, you truly are making a poor decision. You're robbing yourself of some valuable knowledge and experience.

as far as taking game maker as a prototyping tool, you may find yourself frustrated when it doesn't do the one action you really want it to do. If you learn a little bit about javascript or c#, you would actually find unity3d to be a great prototyping tool, especially when you learn about the engine as a whole. It's incredible what you can test with it, from fake battle systems to android flying games. Probably deviated from the discussion a little bit, but I thought it was important to mention.