I know it's a one-of-a-kind game, but it still amazes me that Roller Coaster Tycoon released in 1999, a game where you could have hundreds of NPCs on screen at a time, unique events and sound effects for each of those NPCs, physics simulations of roller coasters and rides, terrain manipulation, and it was all runnable on pretty basic hardware at that time. Today's AAA games could never. I'm glad some indie games are still carrying the torch for small, efficient games that people can play on any hardware though.