From the description: "This is modified version of Derek Yu's game Spelunky Classic. Based on the source code published in Humble Weekly Bundle: Play and Create with GameMaker (not original 1.1 release)." The original game was made in GameMaker 8 (or 7?) and was ported to GameMaker Studio 1.x before the source code was published by Humble Bundle. Lighting implementation wasn't done by me (like many other things), it already was in the source code that I modified. Likely it was hard/impossible to make the same lighting as in the original, I don't know. The current implementation is OK for me.
All content should be here (except for level editor). But I'm not 100% sure because the initial port wasn't done by me, and I never played the game much (original or this version).
The game can be completed, and major bugs are fixed. There are some bugs left, but I can't tell you how much, the game was never properly tested.