In supcom theres a user made map called zone control.
Its a grid of squares, and the corners are raised.
You start with a turret in one square next to a raised square, and in the raised square you have 3 buildings and an upgrader. The turret spawns a unit every 2-3 seconds.
You can upgrade the turret and what it spawns using the units in the raised square, or by killing other units.
Every other square contains a neutral turret that fires at anybody but doesnt spawn units.
You are supposed to attack these turrets and take control of that zone before the enemy, so that a new turret spawns and starts spawning more units for you.
Theres no commander or building factories, no resources of any kind save taking control of turrets.