Bungie's classic shooter Marathon is now available on the iPad, starting at the low cost of zero dollars. Touch Arcade reports that the open source game was taken on as a port project by coder Daniel Blezek, and officially supported by Bungie.

You can play the game for free, but the app offers a few enhancements if you're willing to pay. The standard game includes standard textures, but you can buy a high-res texture pack for $3.99. You can also enable Master Chief mode for 99 cents, which unlocks cheats like all weapons, infinite ammo, invincibility, instant shields, stage select, and saving anywhere. The two packs are in-app purchases.

It relies on a virtual stick with touch-based aiming and on-screen buttons, so those who groan at virtual pads might want to stay away. On the other hand, it's a historical artifact from one of the world's most popular developers, and only costs a bit of time and drive space for the basic settings. If you're an iPad owner, there's no harm in giving the old girl a try.