the game is a great game for the current state right now. here are a list of suggestions i wrote down for further builds
change crates images (reason: i didnt realize they were crates until level 4... lol they didnt look like crates to me) (if you remain having the same image then id suggest adding a glow effect to them so they are more appealing to explore or attempt to shoot at)
add health bars to baddies (npc healthbars are everything in these type of games. as a player you would like to know whats the status of the object your killing. you can make this toggle on or off button aswell with proper scripts and ect)
add sprint ( shift key to do a short sprint)
dmg counter ( how much damage were dealing per shot)
headshots bonus (a bonus when you fire upon npc head)
right click melee (melee for those baddies that are coming towards you as a melee)
music can change each level so its not so repetitive
great job guys and thank you for allowing me to give feedback aswell test your game. lmk if u would like further testing
side note: didnt find any bugs on first play through of all levels