Dots & Boxes by Tamaki is the classic pencil-and-paper game.
Draw a line between two dots. Close the fourth side of a square and you claim that box, then draw again. Most boxes when the paper is full wins.
Play the computer at Easy, Medium, or Hard. Pass one device between two people. Or host an online room and send a 6-character code to a friend.
No accounts. The Android app shows ads. You can pay once through Google Play to remove them. Local play stays on your device.
Draw lines, close boxes, and keep the chain going.