It's not bad, definitely not for a first try. My biggest complaint is that it has that annoying "character slides around as if on ice" effect that I hate. I did like the fact that the coins were necessary to complete the game. Many such games just have pointless collecting of a random item.
The visuals are nice, but as the reviewer says below, Pipa's size compared to a relatively small window is jarring, especially when you're not sure what you're about to jump into. I enjoyed some of the backgrounds. The castle was nice, and the banners in the final chamber (inside the castle?) The music is a tad over-dramatic, and I ended up turning it off.
I found some of the glitches listed by other reviewers, but there are some others. The one the sticks out the most is that Pipa tends to become invincible. More than once, spikes stopped effecting her, which removed all challenge from the game.
I see a lot more you could do to expand the game. Similar games have other collectibles to unlock portions of the maze. For example, you can't get to certain areas without bullets, but you also need high jump to get to other areas, maybe flight, wall-walk, water-walk, spike-walk to get to others. Some story, maybe? Who is this little vegetable girl, and what is she hunting for? Maybe she collects special powers that let her grow beanstalks to climb and flowers to trampoline off of, opening new areas in the game.
This is a good start. What can you do to make it special? As it is, that game feels like a beta to me, but you deserve credit for make a reasonably fun game. The first thing I would do is iron out the glitches, get a good, well-running experience. I like that you're already looking to bigger and better projects. Can't wait to to see what you do next!