Very nice looking game! I really enjoy the fac that there are dedicated cutscenes for each actions which really makes them feel alive.
I dont know if the countdown becomes faster as you defeat more bosses, but I do wish it was there was a way to make it a bit faster (maybe you can hold space to make it go fast?), and i wished for more description for the skills.
I also personally find it a very creative use of the theme Countdown! Most games (including miine) used countdown as something counting down to "game over" but here it uses countdown as a mechanic to attack which I find really unique!