Connect4

Connect4 (Flash Classic) was one of those straightforward games you'd find on a Flash gaming site in the 2000s. It didn't need a big developer name attached to it; it was just there, a digital version of the familiar physical game. You loaded it in your browser, and it was ready to go without any fuss.

You control the game entirely with your mouse. Your turn consists of moving a disc over the top of the seven-column grid and clicking to drop it. The disc falls to the lowest available space in that column. Your main objective is simple: get four of your colored discs in a row, horizontally, vertically, or diagonally, before your opponent does. You have to block their potential lines while setting up your own, which involves looking several moves ahead. The pacing is quick, with turns alternating rapidly, and the difficulty comes entirely from the person or AI you're playing against. It feels like a clean, focused test of spatial planning.