Very useful for every BA beginner:
Cooperative play (co-op)
BA includes a cooperative play mode for players to work as an even closer team. When the cooperative mod option is enabled, players who take the same team id will form a co-op. Players who are part of the same co-op completely share everything - all resources are pooled, and any unit within the co-op can be commanded by anyone within the co-op.
Each player within the co-op starts with their own commander, and must select their own start point before clicking ready - if the co-op readies before a player has selected a start location, then two commanders will spawn on the same spot.
Once the game has started, it is especially important for co-oping players to communicate their overall strategy so that units don't receive conflicting orders. It's also somewhat easier to overspend - in a co-op of three, players might feel like they have triple the normal amount of resources.
In practice, co-op mode tends to work best when done with friends, clanmates, or other (willing) strangers. However, even among voluntary participants experience has shown that large co-ops of 5 or more players tend to have at least one person getting upset due to their orders being canceled or similar (often unintentional) issues. Unless communication can be improved through mumble, it is recommended to split large co-oping teams into multiple, smaller co-ops.
If cooperative mode is disabled, then players who share the same team id will instead share control of the same commander. This is called "comm-sharing" and is available in every mod.
Balanced Annihilation features a chicken defense subversion, designed as a BA version of tower defense.