Islands and sea
Each number is the size of its island. Mark the sea around them, all in one piece.
Example
Example
The 2 in the corner needs one more square. Which one can it take?
Choose a square to see what happens.
Small islands. Finished islands and their edges do most of the work.
A new board every day, at midnight on your clock.
1 board · No time limit
One answer, reached by reasoning alone. No guessing.
How to solve
- Start with the 1s and any finished island: every square along its edge is sea.
- A square that touches two different islands is sea, or they would join.
- Count how far each number can still reach. A square no island can reach is sea.
- Never leave a 2 by 2 block of sea. Three sea squares in a block make the fourth one island.
- Keep the sea in one piece. Sea with one way out goes that way, and a square the sea cannot do without is sea.
Choose Sea or Island, then tap squares or drag across them. Tap a marked square again to clear it. Island marks are optional: the board is solved once the sea is right.
On by default unless you turn it off. Saved choices are kept. Shares starts, completions, replays and error categories. For ChatGPT visits, starts and completions may include the first QuickenBrain page and country. No answers, drawings or names.
How this data is usedHelp
Each number is the size of its island. Mark the sea around them, all in one piece.
- Each island holds exactly one number and has that many squares, counting the number's own square.
- Islands never touch along an edge. They may meet at a corner.
- All the sea joins along edges into one piece.
- No 2 by 2 block is all sea.
Choose a difficulty, then select Start. Hints first show where to look. You decide whether to reveal the reasoning or apply a step. Undo and redo let you revise your work.
Saved on this device
About this practice
Each number is the size of its island. Mark the sea around them, all in one piece.
Report a problem
On by default unless you turn it off. Saved choices are kept. Shares starts, completions, replays and error categories. For ChatGPT visits, starts and completions may include the first QuickenBrain page and country. No answers, drawings or names.
How this data is used