Spelunky is a unique platformer with randomly-generated, fully-destructible levels that offer a challenging new experience each time you play. Journey deep underground and explore fantastic places filled with all manner of monsters, traps, and treasure. You'll have complete freedom while you navigate the fully-destructible environments and master their many secrets. To stay or flee, to kill or rescue, to shop or steal... in Spelunky, the choice is yours and so are the consequences!

More details on the official game page of Spelunky ...