Nice short platformer. Because the theme is count down, I understand that there is a timer. However, I think the timer might not be required. Finishing each of the platform-sections once is satisfying enough, especially for a game jam game. I did not like spending my time walking back towards each challenge when the time is up. Another thing could be to change the "lives going from 10 to 0" to "attempts going from 0 to infinity". Good players will have a low number of attempts, other players can finish it without having to worry about their progress being reset.