The frog, or rather a moth, was supposed to move in jumps. You can predict its movement because it always moves diagonally. It bounces off walls and magma, returning in the other direction, and so on :)
You are certainly right but the distance of each move is too big and so hard to deal with in my opinion. So maybe less distance between this "jumps" would also make the movement a little bit more fluid. It is causing the game to be much more difficult than necessary.
The walking animation should be improved. It is looking very weird.
This is a very nice clone, too: