Sightline0h n0
Every number is a view. Every wall changes it.
Look along the lines
A numbered blue circle must see exactly that many other blue circles along its row and column. Coral walls stop the view. Every blue circle must see at least one other.
Click a blank cell: blue → coral wall → blank. Numbers and small locked walls stay fixed. Fill every cell to finish.
Keyboard: arrows to move · Enter / Space to cycle · B blue · W wall · Delete clear · Z undo.