I couldn't beat the later levels, starting from B+ (I think). Good thing you can still click on the level tiles and play later levels, but those were also kinda buggy TBH - multiple teleporters were spawning hordes of clones and the game decided arbitrarily that that is too much - I got the one you need to stack 2 of you, but the next one was impossible to me.
Other that that - awesome work, cool mechanics and also looks good!