Hello! Welcome to Feedback Quest 8! My name's Hythrain, a co-host and one of the streamers for this event! This feedback is being written live as I stream your game! If you're interested in seeing my live reaction, let me know and I can send you a link to the VOD once it's posted to YouTube!
So my normal approach for any game in these events is simple: I get the game, make sure it's not a virus, then play it with as little information on how to play as possible. This way, I can judge how intuitively someone can figure out the game. Only if it's obvious that I need to read more will I do so. I note this so you can get a sense where some of these feedback comes from. In addition, I want to note that feedback and rating are different; don't use this feedback to gauge what I'll rate, nor should you view my rating as entirely indicative of my feedback.
Here it is, the incredible true story of the 100% not-real Curtle P. Justice!
I would guess this is one of if not your first game. You got the basics down, so now it's time to do a bit more with it. Make enemies the player can defeat, make it possible to lose and try and expand your gameplay. Also make more variation in your platforming instead of it being pretty much just going to the right. When you do get to making more robust stages, always keep in mind how your design is. You don't want to create blind jumps (where a player has to jump from one platform to another but where they can't see the destination until they're already falling) unless you use a trail of collectables for the player to follow OR if the path in question is on a secret upper path and there's little to no chance of the player falling to their death if they jump down to the lower one (they can still get hurt, though, since they've not learned the lower path yet). You also want to ensure that at no point is the player put in a position where they can't proceed without getting hurt; this one you had happen a couple of times.
Since this is a platformer, I recommend taking a look at classic platformers, especially 2D Mario games (Mario 3 on the NES and Super Mario World on the SNES are both great for this). While doing so, pay attention to things like how platforms are designed and how enemies work to see the things I brought up above work. Honestly, watching what Nintendo does with games is often a great way to learn how to make games as they consistently follow good game design.