Oldschool software development kit for games
Hmm, I think that nobody is going to claim that they learned to design a game in this particular software tool, but then again, I think that taking a look at how software development tools evolved will make you more capable of understanding the hurdles game developers have been facing through the years, trying to bring us our favorite entertainment. Anyway, this set of tools allows you to create 3D games, and it is particularly intended for action and adventure 3D games. Of course, noting is going to stop you from making something else completely, after al the buil contains both creation tools as well as scripting tools. While I did spend a bit of time in The Elder Scrolls Morrowind world building toolset and in Painkiller's a bit, I must say that I'm no expert in what makes such a digital tool easy to use, but, at any rate, 3D Construction Kit 2 seems to have enough options, some of which I recognized from these games I just mentioned. What it doesn't have is a more comprehensive library of assets, so you won't be able to just go building your game, you might want to import some or just create them out of scratch. Also, this tool comes with its own compiler, so if you're really serious you can make your own little standalone game. But, I'd suggest you migrate towards Unity if you really want to build a game, a serious game. I mean this tool will only allow you 256 colors in VGA mode type graphics and I'm pretty sure it must have some other (self evident!) limitations.
