If you're on a budget and want to play a classic puzzle/platformer, act quick, as 1997's Oddworld: Abe's Oddysee is free on Steam for the next 24 hours.
The sale isn't restricted to Abe's Oddysee, either. The "Oddworld Pack" includes Abe's Oddysee and Abe's Exoddus for a mere $1.24 for the next 40 hours, while the "OddBoxx" includes the previous two games as well as Oddworld: Munch's Oddysee and Oddworld: Stranger's Wrath HD for $3,24.
Oddworld: Abe's Oddysee was later remastered in HD as Oddworld: New 'N Tasty.