I've rated the game, and here is the constructive criticism as promised. Quite simply put, the game needs some work. There are a few things that you've actually done really well, but some things that definitely need some work.
I'll start with the positive, which is the fact that the game does a beautiful job of communicating everything the player needs to do without directly telling the player what to do. The colours make it clear as day what the player controls, what are obstacles, and what the objective of the game is. Few games are able to pull this off (believe me, a lot of people struggle with this), so you should absolutely give yourself a pat on the back for this. Another example of this in your game are the parabolic arcs that predict where the cube will go, doing a perfect job of communicating to the player exactly how to move and where the cube will move once the mouse is clicked, without ever directly telling the player "this is how to move. these dots show you where the cube is likely to go"
Unfortunately, the buggy nature of the game makes it rather infuriating to control. Yes, the predictive arc of the cube can be really helpful for that player, but this is only if the cube actually follows that arc, which it does not. Fixing the movement of the player will definitely improve the quality of the game by a mile. This shouldn't be a difficult fix, but it's an absolutely mandatory thing to fix if you want a playable game. Maybe even reconsider the controls of the player to control a bit more like Angry Birds does, with the player having to pull back on the cube to launch it forward to add an element of skill to the movement.
The only other issue I had with the game is the audio of the game. Instead of whatever audio you chose for this game, download some royalty free music to be played quietly in the background of the game and a royalty free "bounce" sound or something similar for when the player jumps. Once again, more often than not it's these really small details that can seriously improve the quality of the game.
Once these things are fixed though, you should really consider the direction that you want to take the game if you want to develop it further. Maybe look into some more dynamic interactions, like canons or explosions or breakable walls or many other ways to add more diversity into the gameplay of your game. Right now it's just a really average platformer, so you'll have to think hard about what will make your game unique enough for people to choose to play your game over another one, and what will make your game interesting enough to keep people playing your game. The simple fact of this is that if there's nothing about your game that makes it unique or interesting, people aren't going to play it. I'd suggest spending some time doing some trial and error to figure out what mechanics are fun and do some brainstorming to think of unique mechanics for the game.
If you can work on these things, you'll have yourself a really fun and unique game. I hope this feedback helped! If you have any questions or concerns, don't be afraid to bring them up :)