This is an HTML5 clone of Jelly no Puzzle, an excellent puzzle game that was released for Windows only. The game design and levels are taken directly from that. If you can run the Windows version I highly recommend it as it has a lot of great extra details.

How to play: Hover over a jelly and press left or right to move it. When jellies of the same color touch, they merge. Your objective is to unify all jellies of the same color (except black jellies).

You can also play on a smartphone, by dragging jellies.

Here's the source.