GameMaker: Quick Menu

GameMaker is a specialist 2D game engine that has been in the public domain for nearly 25 years. This makes it one of the longest-running engines on the market at the moment. During this time, some of the best indie games, such as Undertale, Hyper Light Drifter, and Chicory: A Colorful Tale, have been created using GameMaker.

Spelunky is a 2008 platform game developed by Derek Yu that challenges players to explore procedurally generated caverns. The game spawned a sequel and became a cult, critical and commercial success, selling over 500,000 copies.