Very impressive for a first time jammer!
One piece of feedback, and this is on the side of improvement, not a critique really:
Your core Countdown tie in is the microwave flashing to regain HP, I was expectating that moment to keep my run going further, so in this cases where you want the player to have their hopes and focus on it's recommended to add ALL THE POSIBLE JUICE, and by juice I mean signaling visually to the player that the thing is coming.
Aside from than nitpicky feedback everything else is awesome.