feat(combat): rank matches by enemy-kill combat turns

Adds combat_turns metric (distinct turns where ≥1 bot died from enemy
focus-fire, excluding self-collisions). Worker computes it after each
match; index builder sorts matches/index.json and the new most-combat
playlist descending by it, and bumps interest score for combat-heavy
matches so they surface in highlights.

Also switches homepage featured replay default view from influence to
standard so the actual bot-on-bot combat is visible.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/acb-api/db.go

@@ -262,6 +262,13 @@ CREATE TABLE IF NOT EXISTS playlist_matches (
 );
 CREATE INDEX IF NOT EXISTS idx_playlist_matches_playlist ON playlist_matches(playlist_slug, sort_order);
 
+-- Add combat_turns column to matches if it doesn't exist (idempotent migration)
+DO $$ BEGIN
+    IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'matches' AND column_name = 'combat_turns') THEN
+        ALTER TABLE matches ADD COLUMN combat_turns INTEGER NOT NULL DEFAULT 0;
+    END IF;
+END $$;
+
 -- Community replay feedback (plan §13.6, §8.3)
 CREATE TABLE IF NOT EXISTS replay_feedback (
     feedback_id   VARCHAR(32) PRIMARY KEY,

cmd/acb-index-builder/db.go

@@ -38,6 +38,7 @@ type MatchData struct {
 	WinnerID     string             `json:"winner_id,omitempty"`
 	TurnCount    int                `json:"turn_count"`
 	EndCondition string             `json:"end_condition"`
+	CombatTurns  int                `json:"combat_turns"`  // turns with ≥1 enemy-kill combat death
 	Participants []ParticipantData  `json:"participants"`
 	CreatedAt    time.Time          `json:"created_at"`
 	CompletedAt  time.Time          `json:"completed_at"`
@@ -341,6 +342,7 @@ func getBotMatchStats(ctx context.Context, db *sql.DB, botID string) (played, wo
 func fetchMatches(ctx context.Context, db *sql.DB) ([]MatchData, error) {
 	query := `
 		SELECT m.match_id, m.map_id, m.winner, m.turn_count, m.condition,
+		       COALESCE(m.combat_turns, 0),
 		       m.created_at, m.completed_at,
 		       COALESCE(
 		           json_agg(
@@ -364,7 +366,7 @@ func fetchMatches(ctx context.Context, db *sql.DB) ([]MatchData, error) {
 		LEFT JOIN match_participants mp ON m.match_id = mp.match_id
 		WHERE m.status = 'completed'
 		GROUP BY m.match_id, m.map_id, m.winner, m.turn_count, m.condition,
-		         m.created_at, m.completed_at
+		         m.combat_turns, m.created_at, m.completed_at
 		ORDER BY m.completed_at DESC
 		LIMIT 1000
 	`
@@ -383,6 +385,7 @@ func fetchMatches(ctx context.Context, db *sql.DB) ([]MatchData, error) {
 
 		err := rows.Scan(
 			&m.ID, &m.MapID, &winnerID, &m.TurnCount, &m.EndCondition,
+			&m.CombatTurns,
 			&m.CreatedAt, &m.CompletedAt, &participantsJSON,
 		)
 		if err != nil {

cmd/acb-index-builder/generator.go

@@ -81,6 +81,7 @@ type MatchSummary struct {
 	Turns        int                  `json:"turns"`
 	EndReason    string               `json:"end_reason"`
 	Enriched     bool                 `json:"enriched"`
+	CombatTurns  int                  `json:"combat_turns"` // turns with ≥1 enemy-kill combat death
 }
 
 // MatchParticipantSummary represents a bot in a match summary
@@ -313,6 +314,12 @@ func generateMatchIndex(data *IndexData, outputDir string, botNameMap map[string
 		summaries = append(summaries, matchToSummary(m, data, cfg))
 	}
 
+	// Sort matches by combat_turns descending so the most combat-heavy
+	// matches surface first in the UI.
+	sort.Slice(summaries, func(i, j int) bool {
+		return summaries[i].CombatTurns > summaries[j].CombatTurns
+	})
+
 	index := MatchIndex{
 		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
 		Matches:   summaries,
@@ -350,6 +357,7 @@ func matchToSummary(m MatchData, data *IndexData, cfg *Config) MatchSummary {
 		Turns:        m.TurnCount,
 		EndReason:    m.EndCondition,
 		Enriched:     enriched,
+		CombatTurns:  m.CombatTurns,
 	}
 }
 
@@ -642,6 +650,18 @@ func generatePlaylists(data *IndexData, outputDir string, botNameMap map[string]
 				sortByInterestScore(matches)
 			},
 		},
+		{
+			slug:        "most-combat",
+			title:       "Most Combat",
+			description: "Matches with the most turns featuring enemy kills — the bloodiest battles on the grid",
+			category:    "featured",
+			filter: func(m MatchData) bool {
+				return m.WinnerID != "" && m.CombatTurns > 0
+			},
+			sort: func(matches []MatchData) {
+				sortByCombatTurns(matches)
+			},
+		},
 		{
 			slug:        "featured",
 			title:       "Featured Matches",
@@ -1046,6 +1066,12 @@ func interestScore(m MatchData) float64 {
 	} else if cr >= 3200 {
 		score += 1.0
 	}
+	// Combat-heavy matches are exciting
+	if m.CombatTurns >= 30 {
+		score += 2.0
+	} else if m.CombatTurns >= 15 {
+		score += 1.0
+	}
 	return score
 }
 
@@ -1073,6 +1099,12 @@ func sortByCombinedRating(matches []MatchData) {
 	})
 }
 
+func sortByCombatTurns(matches []MatchData) {
+	sortSlice(matches, func(i, j int) bool {
+		return matches[i].CombatTurns > matches[j].CombatTurns
+	})
+}
+
 func sortByInterestScore(matches []MatchData) {
 	sortSlice(matches, func(i, j int) bool {
 		return interestScore(matches[i]) > interestScore(matches[j])

cmd/acb-worker/api.go

@@ -83,6 +83,7 @@ type MatchResult struct {
 	EndReason   string          `json:"end_reason"`
 	Scores      map[string]int  `json:"scores"`
 	CrashedBots map[string]bool `json:"crashed_bots"` // bot_id -> crashed
+	CombatTurns int             `json:"combat_turns"`  // turns with ≥1 enemy-kill combat death
 }
 
 // ConvertDBJobToJob converts a DBJob to Job type.

cmd/acb-worker/db.go

@@ -336,9 +336,10 @@ func (c *DBClient) SubmitMatchResult(ctx context.Context, jobID string, result *
 	_, err = tx.ExecContext(ctx, `
 		UPDATE matches
 		SET status = 'completed', winner = $1, condition = $2,
-		    turn_count = $3, scores_json = $4, completed_at = $5
+		    turn_count = $3, scores_json = $4, completed_at = $5,
+		    combat_turns = $7
 		WHERE match_id = $6
-	`, winnerIndex, result.EndReason, result.Turns, scoresJSON, now, matchID)
+	`, winnerIndex, result.EndReason, result.Turns, scoresJSON, now, matchID, result.CombatTurns)
 	if err != nil {
 		return fmt.Errorf("failed to update match: %w", err)
 	}

cmd/acb-worker/main.go

@@ -389,9 +389,39 @@ func (w *Worker) executeMatch(ctx context.Context, claimData *JobClaimData) (*Ma
 		}
 	}
 
+	// Compute combat_turns: count distinct turns where ≥1 bot died from "combat" (enemy kill)
+	result.CombatTurns = computeCombatTurns(replay)
+
 	return result, replay, nil
 }
 
+// computeCombatTurns counts the number of distinct turns in a replay where at
+// least one bot was killed by an enemy (reason == "combat"). Deaths from
+// self-collision or other causes are excluded.
+func computeCombatTurns(replay *engine.Replay) int {
+	if replay == nil {
+		return 0
+	}
+	combatTurnSet := make(map[int]struct{})
+	for _, turn := range replay.Turns {
+		for _, event := range turn.Events {
+			if event.Type != engine.EventBotDied {
+				continue
+			}
+			details, ok := event.Details.(map[string]interface{})
+			if !ok {
+				continue
+			}
+			reason, _ := details["reason"].(string)
+			if reason == "combat" {
+				combatTurnSet[turn.Turn] = struct{}{}
+				break // one combat death is enough to count this turn
+			}
+		}
+	}
+	return len(combatTurnSet)
+}
+
 // sendHeartbeats sends periodic heartbeats while a match is running.
 func (w *Worker) sendHeartbeats(ctx context.Context, jobID string) {
 	ticker := time.NewTicker(w.heartbeat)

web/src/pages/home.ts

@@ -145,8 +145,8 @@ export async function renderHomePage(): Promise<void> {
   // Featured replay: use demo replay as fallback when no live matches
   const hasLiveReplay = !!featuredReplay;
   const replayEmbedSrc = hasLiveReplay
-    ? `/embed.html?match_id=${featuredReplay!.id}&autoplay=true&speed=150&loop=true&view=influence`
-    : '/embed.html?demo=true&autoplay=true&speed=150&loop=true&view=influence';
+    ? `/embed.html?match_id=${featuredReplay!.id}&autoplay=true&speed=150&loop=true&view=standard`
+    : '/embed.html?demo=true&autoplay=true&speed=150&loop=true&view=standard';
   const replayTitle = hasLiveReplay
     ? `${featuredReplay!.participants.map((p) => `<strong>${esc(p.name)}</strong>`).join(' vs ')}${featuredReplay!.winner_id ? ` — Winner: <strong>${esc(featuredReplay!.participants.find((p) => p.bot_id === featuredReplay!.winner_id)?.name || 'Unknown')}</strong>` : ''}`
     : 'Demo Replay — Watch a sample battle';