A LOOOooong time ago...well 2001-2002'ish (I think). I was playing around a lot with Game Maker by Mark Overmars. There was developer named Brent who went by the handle Freegadgets who made a 3D engine Gadget 3D. It was really quite impressive. He started off by simply remaking a simple version of Doom. Over time he expanded it and eventually it used actual 3D polygons. It was loads of fun to build games with it and very easy. It was also a great learning tool. (As with MANY of my old projects I lost most of the games and models I built during this period).