Nice work!
The fact that you can create multiple clone is very interesting and I can see the game turning into a very nice experience. The art style is also very very nice and so are the sfx.
But there is some problems (that don't destroy the game feel just add up to sour a bit the exprience.)
First of all and it is very minor but happens to easily, if you run in a wall while midair then you will get stuck to it, also the echo is always facing a single direction sadly.
Second I am color blind and I can distinguish the two colors used in lv 2. It not a real problem because it is clear with only 2 platforms but if you want one day make this more of a puzzle game this can get pretty anoying for colorbling people.
Third and most important, the central game mecani is extremelly cool on paper but it is never used in a really great way. Most of the time you will do a platforming section and then wait for your clone to redo it so the door opens. It is kinda sad, maybe you could have gone for a more challenging room where you have to it multiple switches with a echo so it moves platforms up and you need to jump from one to another. Or be clever and use multiple echo and just lift every platforms at once.
Coins can be a great way to provide this sort of challenge and still maintain the cosy feeling and low difficulty of the game.
Don't take this critisism the wrong way, the game is nice and you should be proud of yourself to have finish the project.
Anyway, good day !