Great game, with one glaring flaw.

[Mudvayne]

Great game as title, but the only flaw is when items are on top of portals. It is impossible to pick them up, it just sends you to the next level. Made even worse when you open a chest close to a portal and waste a key. This isn't a major problem in the lower 3 difficulties. But it becomes a major problem early game in the hardest difficulty.