DOOM can now run on a quantum computer with Quandoom port — seminal FPS blood and gore mixed with spooky action

Of course:

The rest of the instructions are all valid n-controlled Toffolis and Hadamards, but of course mostly Toffolis since it's replicating a classical algorithm. There is no quantum advantage, it's just a classical algorithm written in a format compatible with a quantum computer.

Add small errors to the quantum simulator (quantum computers always have those) and all'll break entirely - apparently (1) no error correction was used and (2) it's just logic gates for Doom rewritten as quantum gates. No wonder the author got bored, I'd be bored too.