great feeling momentum based mechanics even with the (mostly) lack of sound effects and music (for the next time i really recommend adding some music even if its just some royalty free songs and spending just a tiny bit more of time on the sfx! it really adds to the experience, just a lil jump sound and a satisfying win sound or jingle when you reach the flag really goes a long way towards making it feel gratifying to play). surprising amount of levels and quality of those levels too! i'd love this if the audio part was more developed and the visuals were a tad bit less repetitive.
as for the theme, i honestly did not understand how it was applied until i read the page afterwards. i cant remember if at any point i died because of the timer ending, maybe i just speedran it lol. but it doesnt really feel like a core mechanic, the core would be the time manipulation, if you wanted the countdown to be an important part of the game i would have added the time left for each level to be on screen at all times, this way it just feels random. shoul'dve been communicated better imo (also as another commenter said, i dont know if it really enhances the experience but i understand its important to fit the theme)
good job!