Sonar

Sonar hides a handful of targets in a dark sea and hands you a single, miserly tool: ping any cell and it answers with one number, the distance to the nearest hidden target — and nothing else. That ping also proves every cell inside that radius empty, so each reading rules out as much as it reveals, and where the distance rings from two or three well-spread pings intersect, a target has to sit. This is deduction, not battleship-style guessing: pinging right next to a target tells you far less than triangulating it from across the grid. The clever part is that marking a cell you have reasoned out scores more than a lucky direct hit, because knowing is the whole point — but three wrong marks end the run, so you only commit when the rings leave one answer. Fewer pings earns a bigger par bonus, rewarding a clean solve over a brute-forced one. Free and instant in your browser, it is a quiet logic puzzle dressed as a submarine.