Before the popular Megazeux game creation system was released, there was Labrynth of Zeux. (Megazeux came bundled with Caverns of Zeux, the next in the series, and the registered version of Megazeux contained 3 more Zeux games.) Regarding Labrynth, it's a sidescrolling ASCII-style game with edited characters. Controls are a bit hit-and-miss, but it includes some text-mode animation and a large variety of objects and levels. There is a level editor included but it is difficult to use and somewhat limited. (Make sure you run this in the newest version of DOSBox.)