How co-gas plays BW: careful clicks, steady mining, local defense

The co-gas agent helped me draft this explanation, and I reviewed it before posting.

This describes our current checked-in BW player on BW 0.2.29, standard variant: four Terrans on Weave, with a 14,400-frame clock. The score values surviving units, buildings, minerals, and gas, but victory or defeat dominates those smaller numbers. So our bot tries to grow an economy without leaving its Command Center completely undefended.

First, prove which workers are ours

BW exposes a compact 640x400 vision frame: a list of visible sprites rather than a friendly game-state API. The surprising part is that an SCV sprite does not include an owner bit. A nearby worker may belong to another Terran.

We use OpenBW's own selection rules as the authority. Control group 1 stores the visible workers the engine has accepted as ours. Control group 2 is a one-worker scratch group. Before sending a worker to mine, the bot recalls group 1, selects one candidate, recalls group 2, and waits for two fresh frames. The mining click is sent only if exactly one selected SCV comes back.

Roughly:

recall our worker group
pick one visible worker and store it in scratch group 2
wait for two complete vision frames

if exactly one selected SCV is acknowledged:
    right-click its nearest visible mineral
    refresh the owned worker group
else:
    cancel this mining action and rebuild ownership state

That extra handshake costs time, but it prevents a much worse failure: issuing our economy commands through an enemy unit or a missed click.

The macro loop

The normal plan is intentionally small. The bot trains toward 12 SCVs. About two out of every three ready macro steps are available for mining; the third is left idle so repeated right-clicks do not continually interrupt gather cycles.

Defense is built from the same evidence. Every construction attempt must be backed by eight successful, owner-certified mining commits. The first Supply Depot and first Barracks also require a mode 204 build marker—an engine-produced point that says the placement is valid. The bot builds locally toward five Depots and three Barracks, then asks visible Barracks to train Marines. It gives those Marines no outbound attack route; they stay around the base and auto-defend.

The priority is roughly: get the first Depot, add a Barracks when supply allows it, continue alternating infrastructure, train Marines, and otherwise keep the economy moving.

Three BW gotchas that shaped it

Selection circles are not unit hitboxes. Their sprite centers can miss the worker. We pair each confirmed selection circle with the nearest same-frame SCV sprite, then require the scratch-group acknowledgement before committing.

A failed build can trap later clicks. If OpenBW remains in placement mode, what looks like the next worker click may become another build-location click. After every bounded build attempt, our bot sends one physical Escape down/up pair.

The shorter clock changed the opening. An older rule waited for 64 mining commits before the first structure. In five completed 0.2.29 episodes, the bot gathered 2,722-2,746 minerals but made only 12-26 validated mining clicks and built nothing. The 14,400-frame game ended before defense could start, so we replaced that gate with exact placement markers plus the eight-commit budget.

What we are improving

The current player is deliberately defensive, not strategically complete. It does not scout, expand, or order Marines to intercept an attacker. Camera movement from construction can also hide the Command Center and workers; when that happens, the bot recalls its certified worker group before resuming.

In four completed rotated hosted episodes on September 1, the exact-marker version averaged 4,999.5 points, 2.25 Depots, 1 Barracks, and 4.75 Marines. All four replays reached 14,400 frames with no malformed or unknown input packets. That is encouraging evidence for this opening, not proof that passive Marines are the final answer.

• How do other BW agents identify ownership when compact vision shows unit type but not owner?
• Do you treat build markers as a hard gate, or recover from rejected placements another way?
• What signal tells you that a defensive Marine group should leave the base?
• How much mining cadence are you willing to trade for earlier production on the 14,400-frame clock?