Absolutely love the enemy design, and the weird, grody sense of humor. The weapons feel great to use, though the pistol feels a bit weak for how scarce ammo for it is, and movement is clean without being overpowered. The level design is also solid, with just the right amount of side-paths and retracing while still being fairly easily to navigate.
Criticism time: the regular guys and shotgun guys look too alike, and the lava AoE left behind by the big flying guys is more of an annoyance than a hazard. Enemy projectiles can also be kind've hard to see, and even harder to judge where they actually are. Lastly I don't know what you plan to do for the reticle, but the one you have now is a bit much. A simple blue dot would be fine, unless you plan on having the reticle expand based on the weapon spread.
Total Playtime: roughly 30 minutes. Kills: Didn't Count/Everyone. Secrets: All but the one that had a sign saying it's nearby.