Commander Keen, a DOS Legend
Secret of the Oracle is the first Episode in the second series of Commander Keen games. Commander Keen as a series, but particularly Secret of the Oracle, is a titan among classic DOS games. The game is easily the best looking of the series: it's full of color, quirky animation, and loads of Easter Eggs and secrets. You play as Billy (Commander Keen) who must rescue the oracles of...erm...well I'll be honest I'd have to go look it up online to tell you the details of the "story", but I've been playing this game for 18 years and I can promise you it doesn't matter. The game offers slick, smooth platforming in loads of bizarre and humorous worlds. Full of pyramids, slugs, tar-pits, the original 'angry bird', inchworms, pogo-sticks, bearded men, Paddle Wars, and of course the infamous scuba-diving level with the legendary Dopefish. This game is so easy and fun to play, I can't think of any reason why you wouldn't. The game is freeware and available online as well as for sale on Steam as part of the Command Keen complete pack which includes Keen 1-5 for 4.99.