This game looks great! Really efficient use of the color palette and limitation, the pixel art is just great. The jump mechanic itself is very well-tuned and satisfying, it is nice and responsive.
The danger obstacles are difficult to see and read on screen. The changing ability over time as the flame dies out is really cool, but it has the consequence of requiring a lot of waiting just to get to the smaller size. With pretty unforgiving difficulty, I imagine many are dying several times to get through each level, so even though you are only waiting a few seconds to change size, it adds up over time and becomes frustrating. The very repetitive music loop exacerbates that as well. The control scheme for the fire shot ability doesn't feel very good, maybe a WASD movement with using the arrow keys to fire the shots might help the player feel more in control.