Before it was a frustrating XBLA game, Spelunky
was a frustrating freeware PC game. And now it's a quietly, addictively frustrating browser game. Using a new version of the Game Maker software in which Derek Yu coded the original game, developer Darius Kazemi ported Spelunky into HTML5, allowing us to link to a playable version right here
The port isn't perfect – current issues include a lack of dark levels, the removal of any (random) level that starts on the right side, and ... no sound. But on the upside, it's Spelunky
in your browser, for free.