Never made it to the boss, but had fun trying!
Really cool that you have multiple playable characters and more so that they are unlockable. Also great that they all have different weapons and feel different to play. I managed to clear lots of rooms but it felt like a battle of attrition (at least at my skill level), so I always ended up running out of resources whilst trading hits with the enemies. I wasn't able to dodge that successfully and the aiming offset took a bit of getting used to but those are small complaints. Took me a while to work out I can toggle the map with 'm' (and thus plan a route to the boss visiting the 'pickup' rooms along the way) but I think I just missed it during the tutorial. Definitely cool that you included a map though, it gives the game a more tactical element! Graphics wise it would have been great if you could make the enemy weapons more distinctive so the player can easily recognise them. I like the cube characters and that you gave the playable ones distinct features.
The SFX and music were both great and its cool that you managed to incorporate a whole backstory, I find the premise interesting (so I would love to find out what happens after beating the boss).