I love this game, and there are 2 main reasons:
1: Footprints. Thank you for the footprints, every game with mazes as a primary mechanic should have you leaving footprints. I never got lost.
2: Gossamer Guns. I thought I was going to hate the auto aim, but it does a couple of cool things. It forces the player to get up close to enemies, putting themselves at risk. And it also doubles as a bit of a radar, helping you find enemies. Tying your ammo to your score was a bit of genius too, It's basically an accuracy bonus with no extra effort.
The falling bit was nice too, good break in gameplay.
I need to play this again with sound, I didn't read about the soundtrack until I was done my first playthrough.