feat: bitpacked and base64 encoded VisitedRooms in player YAML to keep the file human readable

9 files changed, 218 insertions, 24 deletions

diff --git a/internal/game/cmd_score.go b/internal/game/cmd_score.go
index b493e80..59cedb1 100644
--- a/internal/game/cmd_score.go
+++ b/internal/game/cmd_score.go
@@ -174,7 +174,7 @@ func (g *Game) doScore(sess *net.Session) {
 	sep()
 	stats := p.Stats
 	statsLine := fmt.Sprintf("Rooms Explored: %d      Kills: %d      Deaths: %d",
-		len(stats.RoomsVisited), stats.TotalKills, stats.Deaths)
+		stats.RoomsVisited.Len(), stats.TotalKills, stats.Deaths)
 	content(statsLine)
 	content(fmt.Sprintf("APS Nodes Found: %d", len(getKnownApsNodes(p))))
 
diff --git a/internal/game/exit_migrate.go b/internal/game/exit_migrate.go
index 845a6b2..2872f34 100644
--- a/internal/game/exit_migrate.go
+++ b/internal/game/exit_migrate.go
@@ -10,7 +10,7 @@ import (
 // rewritePlayerRoomIDs remaps room-ID-embedded state in a single player per
 // idMap (oldID -> newID): discovered-exit player flag keys
 // (hidden_exit_<id>_<dir>), current RoomID, EnterSeqRoom, MapSymbols keys, and
-// Stats.RoomsVisited keys. Returns whether any field was changed.
+// Stats.RoomsVisited bitset. Returns whether any field was changed.
 //
 // idMap is assumed to be a bijection (see Room.RewriteRoomIDs); the flag-key
 // and int-map rekeys use delete-all-then-set-all so a swap (A<->B) cannot
@@ -32,7 +32,9 @@ func rewritePlayerRoomIDs(p *player.Player, idMap map[int]int) bool {
 	if len(p.MapSymbols) > 0 && rekeyIntMap(p.MapSymbols, idMap) {
 		changed = true
 	}
-	if len(p.Stats.RoomsVisited) > 0 && rekeyIntMap(p.Stats.RoomsVisited, idMap) {
+	next, moved := p.Stats.RoomsVisited.Rekey(idMap)
+	if moved {
+		p.Stats.RoomsVisited = next
 		changed = true
 	}
 	return changed
diff --git a/internal/game/exit_migrate_test.go b/internal/game/exit_migrate_test.go
index 05edea5..f86b85b 100644
--- a/internal/game/exit_migrate_test.go
+++ b/internal/game/exit_migrate_test.go
@@ -21,7 +21,7 @@ func TestRewritePlayerRoomIDsRename(t *testing.T) {
 			30: {Char: "Y"},
 		},
 	}
-	p.Stats.RoomsVisited = map[int]bool{10: true, 40: true}
+	p.Stats.RoomsVisited = player.NewRoomSetFrom(10, 40)
 
 	idMap := map[int]int{10: 100, 20: 200}
 	if !rewritePlayerRoomIDs(p, idMap) {
@@ -53,13 +53,13 @@ func TestRewritePlayerRoomIDsRename(t *testing.T) {
 	if _, ok := p.MapSymbols[10]; ok {
 		t.Error("MapSymbols should not still have key 10")
 	}
-	if !p.Stats.RoomsVisited[100] {
+	if !p.Stats.RoomsVisited.Has(100) {
 		t.Error("RoomsVisited missing key 100")
 	}
-	if !p.Stats.RoomsVisited[40] {
+	if !p.Stats.RoomsVisited.Has(40) {
 		t.Error("RoomsVisited missing unchanged key 40")
 	}
-	if p.Stats.RoomsVisited[10] {
+	if p.Stats.RoomsVisited.Has(10) {
 		t.Error("RoomsVisited should not still have key 10")
 	}
 }
diff --git a/internal/game/map_test.go b/internal/game/map_test.go
index 2fe9c1e..2975551 100644
--- a/internal/game/map_test.go
+++ b/internal/game/map_test.go
@@ -406,7 +406,7 @@ func TestMap3DDisconnectedComponent(t *testing.T) {
 
 	// Player has only visited tower 1. Tower 2 should appear but dimmed (unvisited).
 	sess := &net.Session{Player: &player.Player{
-		Stats: player.PlayerStats{RoomsVisited: map[int]bool{1: true}},
+		Stats: player.PlayerStats{RoomsVisited: player.NewRoomSetFrom(1)},
 		Flags: map[string]any{},
 	}}
 
@@ -429,7 +429,7 @@ func TestMap3DDifferentZExcluded(t *testing.T) {
 	g := &Game{Deps: Deps{World: world.New(dir)}, GlobalFlags: NewGlobalFlagStore()}
 	mg := mapGlyphsForPlayer(false)
 	sess := &net.Session{Player: &player.Player{
-		Stats: player.PlayerStats{RoomsVisited: map[int]bool{1: true, 2: true}},
+		Stats: player.PlayerStats{RoomsVisited: player.NewRoomSetFrom(1, 2)},
 		Flags: map[string]any{},
 	}}
 
diff --git a/internal/game/render_map.go b/internal/game/render_map.go
index 0177595..3f9c4da 100644
--- a/internal/game/render_map.go
+++ b/internal/game/render_map.go
@@ -131,7 +131,7 @@ func buildTinyMap(g *Game, sess *net.Session, roomID int, mg mapGlyphs) []string
 			if rid == roomID {
 				grid[gr][gc] = mapCell{char: '@', spec: atSpec}
 			} else {
-				unvisited := visited != nil && !visited[rid]
+				unvisited := visited != nil && !visited.Has(rid)
 				ch, spec := roomMapSymbol(g, sess, rid, unvisited)
 				if unvisited {
 					spec = dimSpec
@@ -307,7 +307,7 @@ func buildFullMap(g *Game, sess *net.Session, roomID, mapWidth, mapHeight int, m
 		if rid == roomID {
 			grid[gr][gc] = mapCell{char: '@', spec: atSpec}
 		} else {
-			unvisited := visited != nil && !visited[rid]
+			unvisited := visited != nil && !visited.Has(rid)
 			ch, spec := roomMapSymbol(g, sess, rid, unvisited)
 			if unvisited {
 				spec = dimSpec
@@ -409,9 +409,9 @@ func buildFullMap(g *Game, sess *net.Session, roomID, mapWidth, mapHeight int, m
 	return renderMapCells(grid, colorMode, 0, mapHeight, 0)
 }
 
-func roomsVisited(sess *net.Session) map[int]bool {
+func roomsVisited(sess *net.Session) *player.RoomSet {
 	if sess != nil && sess.Player != nil {
-		return sess.Player.Stats.RoomsVisited
+		return &sess.Player.Stats.RoomsVisited
 	}
 	return nil
 }
@@ -457,7 +457,7 @@ type mapRenderCtx struct {
 	g           *Game
 	sess        *net.Session
 	bg          *mapGraph
-	visited     map[int]bool
+	visited     *player.RoomSet
 	currentRoom int
 	atSpec      color.ColorSpec
 	dimSpec     color.ColorSpec
@@ -473,7 +473,7 @@ func (c *mapRenderCtx) nodeSpec(roomID int) color.ColorSpec {
 	if roomID == c.currentRoom {
 		return c.atSpec
 	}
-	if c.visited != nil && !c.visited[roomID] {
+	if c.visited != nil && !c.visited.Has(roomID) {
 		return c.dimSpec
 	}
 	_, spec := roomMapSymbol(c.g, c.sess, roomID, false)
@@ -548,7 +548,7 @@ func (c *mapRenderCtx) isCourseLink(roomA, roomB int) bool {
 // courseColoredCell draws a one-way course arrow using the map_course color
 // (dimmed if either endpoint is unvisited).
 func (c *mapRenderCtx) courseColoredCell(roomA, roomB int, glyph rune) (mapCell, bool) {
-	if c.visited != nil && (!c.visited[roomA] || !c.visited[roomB]) {
+	if c.visited != nil && (!c.visited.Has(roomA) || !c.visited.Has(roomB)) {
 		return mapCell{char: glyph, spec: c.dimSpec}, true
 	}
 	return mapCell{char: glyph, spec: c.courseSpec}, true
@@ -557,7 +557,7 @@ func (c *mapRenderCtx) courseColoredCell(roomA, roomB int, glyph rune) (mapCell,
 // coloredCell applies the shared link coloring logic for bar/arrow glyphs
 // (dim if either endpoint is unvisited, otherwise the gradient average).
 func (c *mapRenderCtx) coloredCell(roomA, roomB int, glyph rune) (mapCell, bool) {
-	if c.visited != nil && (!c.visited[roomA] || !c.visited[roomB]) {
+	if c.visited != nil && (!c.visited.Has(roomA) || !c.visited.Has(roomB)) {
 		return mapCell{char: glyph, spec: c.dimSpec}, true
 	}
 	return mapCell{char: glyph, spec: color.Average(c.nodeSpec(roomA), c.nodeSpec(roomB))}, true
diff --git a/internal/player/player.go b/internal/player/player.go
index 65026e7..fcf274b 100644
--- a/internal/player/player.go
+++ b/internal/player/player.go
@@ -333,8 +333,7 @@ func New(name string) *Player {
 		RoomID:      0,
 		MapSymbols:  make(map[int]MapSymbolData),
 		Stats: PlayerStats{
-			RoomsVisited: make(map[int]bool),
-			MobKills:     make(map[string]int),
+			MobKills: make(map[string]int),
 		},
 	}
 	for _, s := range AllSkills {
diff --git a/internal/player/roomset.go b/internal/player/roomset.go
new file mode 100644
index 0000000..3565bb6
--- /dev/null
+++ b/internal/player/roomset.go
@@ -0,0 +1,109 @@
+package player
+
+import (
+	"encoding/base64"
+	"math/bits"
+
+	"gopkg.in/yaml.v3"
+)
+
+type RoomSet struct {
+	bits []byte
+}
+
+func (rs *RoomSet) Add(roomID int) {
+	if roomID < 0 {
+		return
+	}
+	byteIdx := roomID / 8
+	if byteIdx >= len(rs.bits) {
+		nb := make([]byte, byteIdx+1)
+		copy(nb, rs.bits)
+		rs.bits = nb
+	}
+	rs.bits[byteIdx] |= 1 << (roomID % 8)
+}
+
+func (rs *RoomSet) Has(roomID int) bool {
+	if roomID < 0 {
+		return false
+	}
+	byteIdx := roomID / 8
+	return byteIdx < len(rs.bits) && rs.bits[byteIdx]&(1<<(roomID%8)) != 0
+}
+
+func (rs *RoomSet) Len() int {
+	n := 0
+	for _, b := range rs.bits {
+		n += bits.OnesCount8(b)
+	}
+	return n
+}
+
+func (rs RoomSet) IsZero() bool {
+	return len(rs.bits) == 0
+}
+
+func (rs *RoomSet) Keys() []int {
+	var keys []int
+	for byteIdx, b := range rs.bits {
+		if b == 0 {
+			continue
+		}
+		base := byteIdx * 8
+		for bitIdx := 0; bitIdx < 8; bitIdx++ {
+			if b&(1<<bitIdx) != 0 {
+				keys = append(keys, base+bitIdx)
+			}
+		}
+	}
+	return keys
+}
+
+func (rs *RoomSet) Rekey(idMap map[int]int) (RoomSet, bool) {
+	var next RoomSet
+	changed := false
+	for _, k := range rs.Keys() {
+		newK, ok := idMap[k]
+		if !ok {
+			newK = k
+		} else if newK != k {
+			changed = true
+		}
+		next.Add(newK)
+	}
+	return next, changed
+}
+
+func NewRoomSetFrom(ids ...int) RoomSet {
+	var rs RoomSet
+	for _, id := range ids {
+		rs.Add(id)
+	}
+	return rs
+}
+
+func (rs RoomSet) MarshalYAML() (any, error) {
+	return base64.StdEncoding.EncodeToString(rs.bits), nil
+}
+
+func (rs *RoomSet) UnmarshalYAML(value *yaml.Node) error {
+	if value.Kind == yaml.ScalarNode && (value.Tag == "!!null" || value.Value == "null") {
+		rs.bits = nil
+		return nil
+	}
+	var s string
+	if err := value.Decode(&s); err != nil {
+		return err
+	}
+	if s == "" {
+		rs.bits = nil
+		return nil
+	}
+	b, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		return err
+	}
+	rs.bits = b
+	return nil
+}
diff --git a/internal/player/roomset_test.go b/internal/player/roomset_test.go
new file mode 100644
index 0000000..2b6b9cb
--- /dev/null
+++ b/internal/player/roomset_test.go
@@ -0,0 +1,87 @@
+package player
+
+import (
+	"strings"
+	"testing"
+
+	"gopkg.in/yaml.v3"
+)
+
+func TestRoomSetYAMLRoundTrip(t *testing.T) {
+	stats := PlayerStats{
+		RoomsVisited: NewRoomSetFrom(1, 5, 300),
+		MobKills:     map[string]int{"rat": 3},
+		TotalKills:   3,
+		Deaths:       0,
+	}
+	data, err := yaml.Marshal(stats)
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	out := string(data)
+	if !strings.Contains(out, "rooms_visited:") {
+		t.Fatalf("expected rooms_visited key in output:\n%s", out)
+	}
+
+	var loaded PlayerStats
+	if err := yaml.Unmarshal(data, &loaded); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if loaded.RoomsVisited.Len() != 3 {
+		t.Errorf("Len = %d, want 3", loaded.RoomsVisited.Len())
+	}
+	for _, id := range []int{1, 5, 300} {
+		if !loaded.RoomsVisited.Has(id) {
+			t.Errorf("expected Has(%d) == true", id)
+		}
+	}
+	if loaded.RoomsVisited.Has(2) {
+		t.Error("expected Has(2) == false")
+	}
+}
+
+func TestRoomSetOmitEmpty(t *testing.T) {
+	stats := PlayerStats{}
+	data, err := yaml.Marshal(stats)
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	out := string(data)
+	if strings.Contains(out, "rooms_visited:") {
+		t.Errorf("expected rooms_visited to be absent for empty set:\n%s", out)
+	}
+
+	var loaded PlayerStats
+	if err := yaml.Unmarshal(data, &loaded); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if loaded.RoomsVisited.Len() != 0 {
+		t.Errorf("Len = %d, want 0", loaded.RoomsVisited.Len())
+	}
+}
+
+func TestRoomSetIsZero(t *testing.T) {
+	var zero RoomSet
+	if !zero.IsZero() {
+		t.Error("zero value should be IsZero")
+	}
+	visited := NewRoomSetFrom(1)
+	if visited.IsZero() {
+		t.Error("non-empty set should not be IsZero")
+	}
+}
+
+func TestRoomSetMarshalEmpty(t *testing.T) {
+	var rs RoomSet
+	v, err := rs.MarshalYAML()
+	if err != nil {
+		t.Fatalf("MarshalYAML: %v", err)
+	}
+	s, ok := v.(string)
+	if !ok {
+		t.Fatalf("MarshalYAML returned %T, want string", v)
+	}
+	if s != "" {
+		t.Errorf("MarshalYAML empty = %q, want empty string", s)
+	}
+}
diff --git a/internal/player/stats.go b/internal/player/stats.go
index 82b741c..2b63558 100644
--- a/internal/player/stats.go
+++ b/internal/player/stats.go
@@ -1,17 +1,14 @@
 package player
 
 type PlayerStats struct {
-	RoomsVisited map[int]bool   `yaml:"rooms_visited,omitempty"`
+	RoomsVisited RoomSet        `yaml:"rooms_visited,omitempty"`
 	MobKills     map[string]int `yaml:"mob_kills,omitempty"`
 	TotalKills   int            `yaml:"total_kills"`
 	Deaths       int            `yaml:"deaths"`
 }
 
 func (s *PlayerStats) RecordRoomVisit(roomID int) {
-	if s.RoomsVisited == nil {
-		s.RoomsVisited = make(map[int]bool)
-	}
-	s.RoomsVisited[roomID] = true
+	s.RoomsVisited.Add(roomID)
 }
 
 func (s *PlayerStats) RecordMobKill(mobDefID string) {