Solid jam entry! Congrats on this being your first jam! You submitted something, and not just something! Something that's fun! Good job!
The gameplay is fun, and it's a solid well designed level. It is just one level though... I would have loved to see more levels, because the first one was so fun and puzzling.
Having the Up arrow work as the climbing button was a little weird. My browser took it to mean that I wanted to scroll up, so I couldn't really see what was happening for a second. The shift key for jump is also a little odd, space would have been better imo, but shift worked just fine.
Overall, great first jam entry! And great game overall :)