2×2 intersection clues (sum of numbers in surrounding 2×2):
Tools
Click a tool then click a cell
Players choose all cell colors (except the locked initial hints). The solution must satisfy: row/column numbers (one 1,2,3 each), each color occupies exactly 6 connected cells, and each color contains exactly one 1,2,3. 2×2 clues give the sum of numbers in that 2×2 block.