I really like the look of this game and the pixel art! The ninja theme is also cool!
I think the stamina mechanic is interesting, but ended up really hampering the gameplay for me, since the stamina is depleted for every action you take (including walking). There were several times I had to let the character stand still to recover energy so I could make some of the higher jumps. I am terrible at platforming, so this limitation prevented me from getting too far, but I can appreciate the challenge that you're going for!