That old hypercasual game idea of mine … works as an incremental game?
You are in a submarine underwater, seeing the bottom of the ocean from behind glass. The glass is cracking. Keep repairing it to stay alive as long as possible.
The cracks in your submarine/aquariaum glass are just lines.
You move your mouse over to repair parts of it.
At the start, this is very slow, easily drained, and cracks appear far too quickly.
Upgrades make you better (faster repairs, bigger area, longer lines, stronger glass, special types of fish to help out or not, etc.)