Feels very barebones with the lack of graphics, variety, challenge, etc. but the jumping mechanics do feel decent so you could probably go somewhere with this if you keep working on it.

It works well, the platforming feels right and fair. The core gameplay is solid. 

Now besides the obvious lack of music and sound, the game mostly needs 1/at least one thing to spice up the gameplay (moving blocks, ennemies pushing you, time limit, etc) and 2/ some animations or UI elements to add to the game feel; the square could squish a little when jumping, the timer to be a lot more prevalent, etc. 

As a prototype it does it work, but as you probably know it needs a bit more to be engaging. 

Overall, it has a lot of potential to be way more fun, but it is okay rn. One of the things I liked was the background, and how it was a gradient and it looked like I was climbing all the way to space, although it's very simple it could be much more interesting. Maybe have blocks that kill you along the way, or items that are hard to get but give you something nice like a speed boost or an elevator for five seconds. Making some items or obstacles can make this really fun, as atop trying to beat your high score, you need to be skilled and use the movement (I also liked your movement for how slippery it is) to doge obstacles to get ahead.