I think you have the ground work for something cool. I will say if it's just a prototype then it makes sense for how it functions.
I will say that if you plan to turn it into a full game you may want to look into adding more of a story element. Introducing the player to what's going on in the game. Something easy as the kings fortune was scattered through the castle by an angry wizard & he must collect all the coins before his servants/peasants discover this occurred (aka the reason for the timer). It would give someone more motivation as to why they are doing what they are doing.
The random slowmo and fast speed is a cool idea but no explanation as to why it's occurring and just in random spots left me scratching my head.
On the second level I enjoyed having to time my landing properly but it was VERY confusing and random at times which platforms acted more like a trampoline. I'd suggest switching the art for them to make it more clear that they are not a normal platform.
While a little rough around the edges I did actually enjoy playing this and trying to beat it. Kudos on your hard work & you have the groundwork to create something fun & memorable.