This was fun: the controls are responsive and the combat satisfying. The main thing to improve would be variety as the game became quite repetitive in terms of both level design and strategy. Being a Roguelike I assume there is some randomisation of layout, but apart from bosses most of the rooms seem identical - perhaps some variation could be introduced, like rooms with walls that can be used as cover. At first I played about with different strategies, changing size and weapon, but I soon realised that biggest size plus laser was basically an undefeatable combo so I used that in every room. I got to the end of the game without ever running out of ammo or dying, so the player's stats could definitely be reduced (and loot drops less generous). The corridors between rooms do seem too long, and that was the only reason to shrink so I could get through them faster, although the time is useful for regenerating shield.
Fix those issues and incentivise the player to switch up strategies a bit and this could be a really good game.