battleblock theater

You get gems and golden yarn by playing the game, with gems you can unlock prisoners and the yarn is for weapons.

weapons have different characteristics

prisoners are purely cosmetic

you can buy them in-game with whatever you earn (but in the case of some special prisoners, you have to do special things, i will recommend checking out the behemoth's blog every week (every day, better yet, in case) to see how you can get them)