very cool! A few things to note: being able to attack in vertical and horizontal directions was pretty difficult, so adding diagonals would be good. Some of the walls you can get stuck when moving along side them.
And the coins don't seem to do anything so I'm not sure what the value is to collecting them. A great game start! The boss was cool, but it was also annoying that no hearts dropped while destroying the boss components, and I ran into one because of how the movements lock upon using your attack, and died. It didn't feel worth the long grind back to the boss after that, so maybe just spawning your character outside the boss to start again would be a good idea! At least with the current scope of the game