Dots and Boxes is the paper game everyone played in the back of an exercise book: a grid of dots, players taking turns drawing one line between two adjacent dots, and whoever completes the fourth side of a box claims it and goes again.
It looks trivial and isn't. The end game is about chains — long runs of boxes that whoever is forced to open must hand to their opponent — and playing it well means deliberately sacrificing boxes to control who opens what.
Declining to take the last two boxes of a chain, so your opponent is forced to open the next one instead. Giving up two boxes to control who opens a chain of ten is usually a winning trade.
Small grids are, and the theory around chains and parity is well developed. In practice, understanding chain control beats almost any opponent who is just taking boxes greedily.
Yes — tap between dots. Nothing to install.