16 episodes of story-based progression
Machine Attacks is the only story based gamemode in Team Fortress 2. However, not many know of this gamemode due to the nature of bad English used and the poor level design.
Premium Upgrades is a special feature only available on Machine Attacks maps which offer extended upgrades for players.
This is an upgraded upgrades station for Mann vs Machine which provide a wider variety of upgrades and increases the maximum level for every upgrade.