How do I beat the rolling cube boss?

[BCS]

He's really tough...

[Groen90]

I tried to bait him into rolling to the side while his eye was looking towards the bottom, then when he fired I quickly rolled down and to the right and shot the arrow diagonally up to the left towards his eye...
But I've also seen someone do it while facing him, just when he was opening the eye. Doesn't matter if you're in his line of sight, as long as the arrow hits first it's your win.

[goth2191]

Just stay in same exact spot you are when you enter the room, shoot your arrow (but don't retrieve it immediately) and then wait there, when the boss begins moving towards you retrieve the arrow (if you do it too early the arrow is not gonna hit the eye of the cube (when the eye is facing in the same direction that you are facing), and if you do it too late you are gonna get crushed), that way you can kill it just before it kills you.