Like the other play testers, I found this way too difficult. HOWEVER, I have to give kudos for the well-tuned controls. This game is very difficult, but it is close to feeling like it's mostly my fault when I fall or miss a jump. That's a good sign! So why is it "too" hard and who decides? Well, you've got three people saying that. "Too hard" can either mean "this kind of game is not for me", "the game is fighting me and I feel like I can't win", or something else. It's very subjective! I think for this group it's a little bit of both. The reason I say that it's close to feeling right is that there's not that much of an indicator to follow, so you're largely going based on muscle memory and practice. Since that's the case, starting the game with a much easier level might be better. For example, just a few platforms. continue ramping up the difficulty as you go. Your current game is like the ultra hard last level.

I think you should also ask yourself what experience you want the player to have. You were focused on speed running, so do you know anyone who speed runs? What do they think of the game?

Remarkable:
The fine manipulation of velocity needed to succeed in this game (fine manipulation I did not have)
is an interesting mechanic to play with. That mechanic is used in a lot of marble games I've come
across, which admittedly isn't a lot but making the player manipulate the velocity of the ball
just to navigate the course in a timely manner puts an interesting challenge in front of the
player.

Improvement:
The platforms were far too small. I know that may have been intentionally designed that way to
present yet another challenge, but I would look into other games that utilize the principles
you were trying to achieve for improving your level design.

Successful:
The timer was implemented very well, providing the only incentive for moving quickly. The controls
were somewhat tight, but still provided the challenge that you were looking for in terms of a ball
shaped player. The topic was bouncing balls, and I think the way you went about it was very well done.

General:
I disliked the message printed in the console, it was somewhat patronizing even if it was more meant as
an encouragement to do better. I also disliked how small the platforms were as it made the game
ridiculously difficult. Talking about the difficulty, I have to say I liked how tight the respawn
mechanic was and the fact that there was a clear halfway point so well done there. Work on the level
design and you will be that much closer to having a solid rage game under your belt.

• Something remarkable (i.e. you noticed it because it showed care by the developer, was particularly engaging or fun, or was otherwise memorable)
  • I love how you're trying to make the next popular speed run game.  It has the potential to become very interesting and big with some more engaging objects and a little bit more obstacles. 
• Something to be improved about the game
  • I would definitely love to see more things added to the game, seems a bit too simple in terms of playthrough.  Whether it is creating a nice visual background, different sized shapes, or multiple levels, the game could be very fun!
• Something successful about the game
  • When the ball lands on a platform, it can immediately jump again to another platform, adding to the speed run concept and giving the user the ability to consistently jump onto different platforms. The timer also works very well and the restart when the ball falls off a platform and into the abyss. 
• Some general, off-the-cuff feedback (what you liked/disliked and why)
  • Liked: I really enjoyed the speed run concept, it gives you a sense of thrill and accomplishment when you land on each block. I also liked the little tiny addition of the different colored block that indicated the halfway point and the finish line and I liked how each ball restart was nice and clean.
  • Disliked: I am atrocious at keyboard and mouse so this game was outlandishly difficult for me and I can barely make it to the blue platform without restarting over 10 times haha. I would also recommend just changing the platforms around and experimenting with some cool level designs!