Disconnect Four

New puzzle on difficulty
Size: x

Guess | Accept | Reject | Ignore

The goal of this puzzle is to fill in every square with a red or blue piece, so that there are no lines of four pieces of the same color in a row, vertically, horizontally, or diagonally.

Click on a square to place a piece in a square or remove one. Squares with a grey background are clues and can't be changed. If you make a four-in-a-row, you will see a line through those pieces. If you solve the puzzle, a green border will appear.

All puzzles are randomly auto-generated and have a unique solution. There are three difficulty levels: To try a guess, hit the Guess button, and it will keep track of the initial guess you make (green) and everything you can deduce from that (yellow). Then:
This vevrsion is by Michael Gottlieb, 2017. I first saw this type of puzzle in the iOS app "Logic Games" by Andrea Sabbatini.