Seven by seven of open water, four ships to hide (4 · 3 · 3 · 2). Your big ships wear armor — the rival's first shot on them just clanks off, and it has to come back to pierce. The rival hunts with a rotating radar beam that never wastes a sweep on water it already knows. Sink its fleet before your hulls rest.
v2.0 — armor + radar sweep
Tap cells to set ships · Rotate (R) · Undo (U)
Then tap the enemy waters to fire a coordinate.
Arrow keys aim · Enter fires · the board is all you get.