The original version of Towerfall mates the pixel-heavy aesthetic so popular with indie game developers with frantic, four-player multiplayer combat. In lieu of guns and a series of corridors, players are each given archery equipment, then dropped into a 2D stage rife with platforms and pitfalls. Think of it as a cross between the frantic combat of the Super Smash Bros. games, and the exacting, retro platforming and chunky aesthetic of Spelunky.
Towerfall Ascension improves upon this basic template by adding 50 new Versus arenas, "a bunch of new variants" for the game's stages and a few new power-ups. Additionally, Ascension brings with it a new Quest Mode that allows two players to cooperatively battle waves of monsters spawned from portals. The gameplay here is similar to that seen in the game's core multiplayer modes, but as designer Matt Thorson notes, Quest Mode fleshes out Towerfall as a whole by adding "a bunch of new content to explore even when you don't have three friends around."
As of now there is no price point attached to Towerfall Ascension. That March 11 release date only applies to the United States, but Thorson claims that a European release "shouldn't be far behind."