(Purchased on Steam.)
Gorgeous pixel art, smooth and fast-paced dodgeball-esque gameplay, with a mix of relaxing and riveting electronic BGM. Regular mode ('Arcade Arena') is frantic fun in multiplayer, Merlinball is an arguably even more awesome team-based secondary mode!

Trials mode quickly gets a bit over-the-top with the powerups, but can still be a nice diversion for some players; I wouldn't get this game with the intention to play that particular mode.

Oh yes, it runs flawlessly on Linux. Consider getting it on sale if you play alone and like what looks like frantic magical dodgeball / Quidditch, definitely consider it if you plan on doing some local multiplayer sessions!