Flood the tower room by room and float your raft to the lamp room
A cutaway stone tower stands open to view, floor upon floor of chambers, and somewhere high above it the relic waits in the lamp room. Your raft sits at the bottom. The only way up is water.
Tap a room and its sluice hatch swings open. Green water pours through from any full neighbouring room, spreading sideways and climbing upward, and your raft rises with it. Open the right chamber at the right moment and the flood carries you a whole floor higher. Open the wrong one and you have simply poured away something you cannot get back, because the hatches are one-way: water never drains, and nothing you flood can be undone.
Every level hands you a tight surge budget, and the tower is built to waste it. Silted rooms drink far more than their size suggests, swallowing surge that should have lifted you. Sealed hatches refuse to open at all until a neighbouring chamber is already full, so some routes exist only after you have prepared the room beside them. The order of your taps matters as much as the choice, and a chain that looks generous at the first floor can leave you stranded two floors short of the lamp.
So you read the tower before you touch it. You trace where the water will run once it is loose, count which chambers feed which, decide which silted room is worth the cost and which is a trap dressed as a shortcut. Then you commit, hatch by hatch, and watch the level fill towards the plan you made.
Fifteen towers make up the climb, each one a different arrangement of chambers, sealed hatches and silt. The early ones teach the flow of the water; the later ones are tangles where a single misplaced tap is the whole level. Nothing is hidden from you — the full cutaway is there on the screen from the first second, the entire puzzle visible at once. The difficulty is not in discovering the tower but in solving it.
Quiet, deliberate and easy to pick up for a few minutes at a time: one tap to open a hatch, one rising raft, one relic at the top of the lamp room.