I like the atmosphere and the low gravity jumps. For some reason, it just makes sense for a game about collecting balloons. I think it was intuitive enough that the goal was to collect the balloons, but for someone who didn't read the description, it may not be clear that you need to reach the door (the door didn't look like an exit).
Overall I think the concept is good, but there are some clarity problems. For me, the text for the amount of balloons collected was extremely small and I did not know how many balloons I needed to proceed. I also did not know what the items besides the balloon does. The spikes and the door also weren't that clear since they looked like they were part of the background. I like the sound of the balloon popping when touching the spikes.