Root cause of zero combat deaths: bots spawned inside the final zone.
On 40x40 grid, bots spawned at ~5 tiles from center but zone min radius
was 3 tiles. Zone only pushed bots 2 tiles toward center - not enough to
force them within attack range (6 tiles).
Fix: Calculate spawn radius as absolute tile distance from center, then
convert to percentage of grid half-size:
- 2-player: spawn at 10 tiles from center (was ~5 tiles)
- 3+ player: spawn at 8 tiles from center (was ~6 tiles)
When zone shrinks to minimum (radius 3 for 2p, 1 for 3+), bots are
forced within attack range of each other, triggering focus-fire combat.
Test: Unit tests verify spawn distance > zone_min_radius for all player
counts. Manual test shows combat_death events now occur.
Closes: bf-52mn
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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