Very fun game; I loved it! However, the game may need some tweaks.

I'd suggest more settings to improve individual experience and performance (changing the FOV, resolution, etc.) and accessibility settings, like reducing screen flashes/strong screen FX and highlighting enemies (because they are the same color as the scenario).

Speaking of performance, I had some lag spikes while playing, and I have a decent PC (5th gen Ryzen 7 and 16 GB of RAM, but no GPU). The game has pretty simple graphics, so maybe it's the particles that are causing the lag spikes; not sure, though.

Changing the color palette would be good so you don't have a headache while playing, even though the high-contrast yellow matches the game's art style. I think giving the player a color wheel could be an adequate solution, but offering color palette presets would work too.

Also, removing or reducing the scale of the combo indicator on the left side of the screen would be great, as it can distract the player (it consumes a good part of your vision).

Ah, and it seems to have a problem with the dialogue with the Security. The game doesn't let you go through the lines yourself, and they make you wait A LOT between the characters lines, so I'm pretty sure it's a bug.

Besides any of that, HEADACHE is a nice game. Very fun to play and very consistent within its design choices. It's a fast-paced game with a unique style and a lot of room for improvement.

The replayability undeniably does aggregate with the game's general idea, and investing in such a good project would certainly improve the game's concept.