Good work. It's more on the casual side for my personal tastes, but that's just cause I play way too many of these sort of games. The levels have a nice sense of flow, and I liked the secret path.
That said, I noticed the pixel platformer pack is CC0, meaning it is allowed to edit the contents when using them in your own games. The reason I mention that is the cactus didn't look dangerous to me, so I thought it was part of the background at first. I think making the border some shade of red would've helped.