Pretty simple concept for the theme, but the execution is done really well on the small details, like the sfx and the little shakes the other shapes does to indicate that the current shape you are dragging can be matched to them. Could probably be better if there were some piano music or something. For the number part, I suggest having an alternate counter that is shown in smaller text or on hover that show either how many paths is connected to this vertex or how many paths left are there left to connect. Well done.