The developer (Remar Games for Ludosity) put a lot of effort into emulating the 90s DOS shareware experience. The color palette's only 16 colors, the sound effects are simple PC speaker effects, and the frame rate is only 16fps (with an alternate 32fps "smooth mode"). You can read about these efforts on the Ludosity Blog (Part 1, Part 2, Part 3, Part 4).
So far I've only played the first episode,but I'm really enjoying it so far. The gameplay reminds me more of the original Duke Nukem than Commander Keen (the other commonly stated inspiration) as there's no overworld map and there's weapon upgrades available.
