NAIR : Platform Fighters :: Divekick/Footsies : 2D Fighting Games
While the game's only move is a neutral air attack (which the game comically includes a hitbox viewer for), there's a surprising amount of nuance to the movement, including fastfalls, dashdancing, wall jumps and wavedashing. The way the game handles health is also really cool; for each hit you make, you move your own healthbar into the opponents side, allowing for the pace of the match to literally go back and forth.

P.S. it's the price of a coffee and it's got rollback