Spelunky, Made With GameMaker

Spelunky is an exploration treasure-hunting game inspired by classic platform games, developed by Mossmouth. Grab as much treasure from the cave as possible.

Temporarily free: GameMaker Studio, the engine for Hotline Miami

GameMaker Studio 2 - MacLife

One Man, One Mission: Play Spelunky at Work - Giant Bomb

Spelunky, The Independent Games Wiki

Spelunky GameMaker source code available to download - Polygon

Spelunky – Hardcore Gaming 101

Spelunky, Made With GameMaker

Spelunky, The Independent Games Wiki

Spelunky 2