One thing we don't like is the betting range. You jump directly from 0.30 to 1.50 and then to 3 to 7.50 and then jump up. A larger range will make it easier to upgrade after a big win. Now, you will get an extended wildness on reel 2, which will move to reel 3, then wrap 4, and then return to reel 2 after each rotation.
Similarly, the scattering is fast and loose, and it is not impossible to re-trigger 15 free spins. We re-triggered 4 free spins, so we can say for sure that it happened.