Plain Metal Driller has strange gravity and wonky physics. i found it frustrating but addictive when my drill gets wonky at the worst moments.
Hold or release to descend deeper, the physics are wonky and your drill might refuse to cooperate.
The controls are just a tap or click to initiate the drill. Timing is everything, which is kinda weird anyway, because you need to hold or release at the right moments.
Watch how your character leans during drilling. Most leaning slightly can stabilize your descent and save you from misfiring the drill.
Q: What are the controls? A: Tap or click to initiate the drill, hold or release to descend.
Q: What is the objective? A: Not stated.
Q: What is a stated feature? A: Wonky physics.
Q: What is the main mechanic? A: Drilling and descending with timing.