This is a really clever idea! And a really ambitious one for your time frame.
The first stage you encounter spikes on (Stage 6 I think?) killed me like 30 times, I just wasn't being lifted with the ground and would just die as it moved up through me. Up until that point I wasn't having too many issues as long as I was cautious around edges. It was a really good idea to include a skip level feature.
Other than a little roughness with the collision, I really enjoyed it. The movement of the levels was kind of mesmerizing, I kept asking myself, "is the solid ground moving or is the empty space moving?"