Pretty damn fantastic. Simple game with very simple mechanics and super fun to play. The slow-mo plus basic guns gives you lots to try.
The biggest flaw holding it back are the spray patterns on guns and the unreliable aim. Your bullets don't start off accurate on even the first shot (even when standing still) and I noticed they all seem to favor spraying into the far right on the reticle. This makes you miss crucial shots in otherwise perfectly timed moments even at closer ranges. The intention here might be to make you prioritize close, point-blank shots. But even then, the accuracy still feels more than unreliable.
The iron sights also seem misaligned and a bit faulty - moving around will make the model permanently sway into a whole different angle unless you re-aim the sights. The MP5 ironsights are misaligned for the entire game and the bullets travel much higher than your iron sights.
Otherwise, small QOL additions like hit markers, damage indicators (or damage sounds) and maybe more movement options would be amazing. The health and time UI could maybe communicate better? It took me several tries until I realized the red was your damage filling up instead of telling you your remaining health lol.
There's a great game here that has the potential to go fully standalone shooter if the gunplay gets more attention. Speedrunners and arena shooter fans would eat this up so fast with a leaderboard function. Keep it up!