Spring

An RTS engine in the mould of Total Annihilation (and is consequently very similar to Supreme Commander).

Not only does it play host to a wide variety of very polished Real Time Strategy games, it's a Supreme Commander alternative for those who don't have the cash to upgrade their computers to the required specs.

It can be found online here.

The setting contains examples of:

 * Artificial Brilliance: one of the reasons for Spring's development was to enjoy Total Annihilation games without its incredibly stupid AI. Accordingly, the Spring computer player is advanced enough that it can use basic tactics quite effectively, and is very efficient at using available resources. Players used to Total Annihilation skirmish games will quickly be surprised as the AI steamrolls their base with an avalanche of heavy tanks.
 * BFG: being very focused on player-made modifications (both made for Total Annihilation and explicitly for Spring), there's often an emphasis on huge weapons, or units with so many barrels they look more like church organs than cannons.
 * Game Mod: so much so that the stock version of Spring is based on a gameplay modification for the original game. If you want the original unmodified Total Annihilation gameplay you'll have to download a Game Mod for the Game Mod that brings the original stats and units back.
 * Wreaking Havok: particularly powerful explosions deform the terrain. By itself this is little more than a cool effect, but if you launch enough nukes in one place you can form a pit that goes down to the water level. With enough patience (and enough nukes), this can be exploited to create artificial land barriers.