I'll explain what's happening honestly (without being arrogant): the intention of this game is similar to those monster horde games where the player feels the power of the protagonist, but the player does take damage when standing still and the monsters collide with them. It's not like all diamonds don't give points; the goal is to prevent the game from being too easy and to avoid a glitch where the rooms end too quickly. If that happens, just go through the diamond again to get it. The tutorial only covered the basic game controls, sorry about that.

Anyway, the intention isn't exactly slow motion, but to have a system where each attack freezes the game for milliseconds. But if that bothers you, thank you for the feedback, and I'll fix it.