Very cool style and music. For me personally way too tough though. I think the idea of attacking every 10 seconds is interesting, but the massive HP bar of the enemies discouraged me from trying more that 5 times. I think the game could benefit from multiple smaller enemies placed around the screen, which one can kill after 1-2 hits. That way the player would also feel further progression as the level becomes easier and one can start focusing on the boss. Other than that, great work!