Clonk Rage is described as 'Real-time multiplayer game. Players can download more than 47475 maps at ccan.de'. There are three games similar to Clonk Rage for a variety of platforms, including Linux, Mac, Windows, Steam and Android. The best alternative is Terraria. It's not free, so if you're looking for a free alternative, you could try OpenClonk or Clonk.
Clonk is an entertaining, action-packed game of strategy, tactics, and skill. It can be played by a single player, with up to four players on one computer, or any number of players in local networks or via internet.