Taxi Driver Simulator
Popo Singer is a game where gravity matters. I found the guitar collection is the core mechanic.
You must avoid spikes and enemies while jumping, Fast.
The game has a simple jump mechanic. The goal is to collect guitars, which is kinda weird anyway.
You must avoid foes and spikes.
Quick tip from my playthrough: i focus on timing jumps. It is better then just running blindly.
Q: What is the objective? A: Collect guitars.
Q: What is the main mechanic? A: Guitar collection.