fix: 13 bugs found via systematic code review and testing

Multiplayer:
- Add WaitingScreen between class select and game start; previously
  selecting a class immediately started the game and locked the room,
  preventing other players from joining
- Add periodic lobby room list refresh (2s interval)
- Add LeaveRoom method for backing out of waiting room

Combat & mechanics:
- Mark invalid attack targets with TargetIdx=-1 to suppress misleading
  "0 dmg" combat log entries
- Make Freeze effect actually skip frozen player's action (was purely
  cosmetic before - expired during tick before action processing)
- Implement Life Siphon relic heal-on-damage effect (was defined but
  never applied in combat)
- Fix combo matching to track used actions and prevent reuse

Game modes:
- Wire up weekly mutations to GameSession via ApplyWeeklyMutation()
- Implement 3 mutation runtime effects: no_shop, glass_cannon, elite_flood
- Pass HardMode toggle from lobby UI through Context to GameSession
- Apply HardMode difficulty multipliers (1.5x monsters, 2x shop, 0.5x heal)

Polish:
- Set starting room (index 0) to always be Empty (safe start)
- Distinguish shop purchase errors: "Not enough gold" vs "Inventory full"
- Record random events in codex for discovery tracking

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/class_view.go

@@ -36,6 +36,8 @@ func (s *ClassSelectScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd)
 				if room != nil {
 					if room.Session == nil {
 						room.Session = game.NewGameSession(ctx.Lobby.Cfg())
+						room.Session.HardMode = ctx.HardMode
+						room.Session.ApplyWeeklyMutation()
 					}
 					ctx.Session = room.Session
 					player := entity.NewPlayer(ctx.PlayerName, selectedClass)
@@ -44,11 +46,8 @@ func (s *ClassSelectScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd)
 					if ctx.Lobby != nil {
 						ctx.Lobby.RegisterSession(ctx.Fingerprint, ctx.RoomCode)
 					}
-					ctx.Session.StartGame()
-					ctx.Lobby.StartRoom(ctx.RoomCode)
-					gs := NewGameScreen()
-					gs.gameState = ctx.Session.GetState()
-					return gs, gs.pollState()
+					ws := NewWaitingScreen()
+					return ws, ws.pollWaiting()
 				}
 			}
 		}

ui/context.go

@@ -16,4 +16,5 @@ type Context struct {
 	Store    *store.DB
 	Session  *game.GameSession
 	RoomCode string
+	HardMode bool
 }

ui/game_view.go

@@ -86,6 +86,15 @@ func (s *GameScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 			}
 		}
 
+		// Record codex entries for events
+		if ctx.Store != nil && s.gameState.LastEventName != "" {
+			key := "event:" + s.gameState.LastEventName
+			if !s.codexRecorded[key] {
+				ctx.Store.RecordCodexEntry(ctx.Fingerprint, "event", s.gameState.LastEventName)
+				s.codexRecorded[key] = true
+			}
+		}
+
 		s.prevPhase = s.gameState.Phase
 	}
 

ui/lobby_view.go

@@ -41,6 +41,12 @@ func NewLobbyScreen() *LobbyScreen {
 	return &LobbyScreen{}
 }
 
+func (s *LobbyScreen) pollLobby() tea.Cmd {
+	return tea.Tick(time.Second*2, func(t time.Time) tea.Msg {
+		return tickMsg{}
+	})
+}
+
 func (s *LobbyScreen) refreshLobby(ctx *Context) {
 	if ctx.Lobby == nil {
 		return
@@ -71,6 +77,11 @@ func (s *LobbyScreen) refreshLobby(ctx *Context) {
 }
 
 func (s *LobbyScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
+	switch msg.(type) {
+	case tickMsg:
+		s.refreshLobby(ctx)
+		return s, s.pollLobby()
+	}
 	if key, ok := msg.(tea.KeyMsg); ok {
 		// Join-by-code input mode
 		if s.joining {
@@ -132,6 +143,7 @@ func (s *LobbyScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 						room.Session = game.NewGameSession(ctx.Lobby.Cfg())
 						room.Session.DailyMode = true
 						room.Session.DailyDate = time.Now().Format("2006-01-02")
+						room.Session.ApplyWeeklyMutation()
 						ctx.Session = room.Session
 					}
 					return NewClassSelectScreen(), nil
@@ -139,6 +151,7 @@ func (s *LobbyScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 			}
 		} else if isKey(key, "h") && s.hardUnlocked {
 			s.hardMode = !s.hardMode
+			ctx.HardMode = s.hardMode
 		} else if isKey(key, "q") {
 			if ctx.Lobby != nil {
 				ctx.Lobby.PlayerOffline(ctx.Fingerprint)

ui/model.go

@@ -110,6 +110,7 @@ const (
 	screenTitle screen = iota
 	screenLobby
 	screenClassSelect
+	screenWaiting
 	screenGame
 	screenShop
 	screenResult
@@ -129,6 +130,8 @@ func (m Model) screenType() screen {
 		return screenLobby
 	case *ClassSelectScreen:
 		return screenClassSelect
+	case *WaitingScreen:
+		return screenWaiting
 	case *GameScreen:
 		return screenGame
 	case *ShopScreen:

ui/model_test.go

@@ -111,14 +111,22 @@ func TestClassSelectToGame(t *testing.T) {
 		t.Fatalf("should be at class select, got %d", m3.screenType())
 	}
 
-	// Press Enter to select Warrior (default cursor=0)
+	// Press Enter to select Warrior (default cursor=0) → WaitingScreen
 	result, _ = m3.Update(tea.KeyMsg{Type: tea.KeyEnter})
 	m4 := result.(Model)
 
-	if m4.screenType() != screenGame {
-		t.Errorf("after class select Enter: screen=%d, want screenGame(3)", m4.screenType())
+	if m4.screenType() != screenWaiting {
+		t.Fatalf("after class select Enter: screen=%d, want screenWaiting(%d)", m4.screenType(), screenWaiting)
 	}
-	if m4.session() == nil {
+
+	// Press Enter to ready up (solo room → immediately starts game)
+	result, _ = m4.Update(tea.KeyMsg{Type: tea.KeyEnter})
+	m5 := result.(Model)
+
+	if m5.screenType() != screenGame {
+		t.Errorf("after ready Enter: screen=%d, want screenGame(%d)", m5.screenType(), screenGame)
+	}
+	if m5.session() == nil {
 		t.Error("session should be set")
 	}
 }

ui/nickname_view.go

@@ -45,7 +45,7 @@ func (s *NicknameScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 			}
 			ls := NewLobbyScreen()
 			ls.refreshLobby(ctx)
-			return ls, nil
+			return ls, ls.pollLobby()
 		} else if isKey(key, "esc") || key.Type == tea.KeyEsc {
 			s.input = ""
 			return NewTitleScreen(), nil

ui/result_view.go

@@ -35,7 +35,7 @@ func (s *ResultScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 			ctx.RoomCode = ""
 			ls := NewLobbyScreen()
 			ls.refreshLobby(ctx)
-			return ls, nil
+			return ls, ls.pollLobby()
 		} else if isQuit(key) {
 			return s, tea.Quit
 		}

ui/shop_view.go

@@ -25,10 +25,15 @@ func (s *ShopScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 		case "1", "2", "3":
 			if ctx.Session != nil {
 				idx := int(key.String()[0] - '1')
-				if ctx.Session.BuyItem(ctx.Fingerprint, idx) {
+				switch ctx.Session.BuyItem(ctx.Fingerprint, idx) {
+				case game.BuyOK:
 					s.shopMsg = "Purchased!"
-				} else {
+				case game.BuyNoGold:
 					s.shopMsg = "Not enough gold!"
+				case game.BuyInventoryFull:
+					s.shopMsg = "Inventory full!"
+				default:
+					s.shopMsg = "Cannot buy that!"
 				}
 				s.gameState = ctx.Session.GetState()
 			}

ui/title.go

@@ -50,7 +50,7 @@ func (s *TitleScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 			}
 			ls := NewLobbyScreen()
 			ls.refreshLobby(ctx)
-			return ls, nil
+			return ls, ls.pollLobby()
 		} else if isKey(key, "h") {
 			return NewHelpScreen(), nil
 		} else if isKey(key, "s") {

ui/waiting_view.go

@@ -0,0 +1,119 @@
+package ui
+
+import (
+	"fmt"
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+)
+
+// WaitingScreen shows room members and lets players ready up before starting.
+type WaitingScreen struct {
+	ready bool
+}
+
+func NewWaitingScreen() *WaitingScreen {
+	return &WaitingScreen{}
+}
+
+func (s *WaitingScreen) pollWaiting() tea.Cmd {
+	return tea.Tick(time.Second, func(t time.Time) tea.Msg {
+		return tickMsg{}
+	})
+}
+
+func (s *WaitingScreen) startGame(ctx *Context) (Screen, tea.Cmd) {
+	room := ctx.Lobby.GetRoom(ctx.RoomCode)
+	if room != nil && room.Session != nil {
+		ctx.Session = room.Session
+		ctx.Session.StartGame()
+		ctx.Lobby.StartRoom(ctx.RoomCode)
+		gs := NewGameScreen()
+		gs.gameState = ctx.Session.GetState()
+		return gs, gs.pollState()
+	}
+	return s, s.pollWaiting()
+}
+
+func (s *WaitingScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
+	switch msg.(type) {
+	case tickMsg:
+		// Check if all players are ready → start game
+		if ctx.Lobby != nil && ctx.Lobby.AllReady(ctx.RoomCode) {
+			return s.startGame(ctx)
+		}
+		return s, s.pollWaiting()
+	}
+
+	if key, ok := msg.(tea.KeyMsg); ok {
+		if isEnter(key) && !s.ready {
+			s.ready = true
+			if ctx.Lobby != nil {
+				ctx.Lobby.SetPlayerReady(ctx.RoomCode, ctx.Fingerprint, true)
+				// Solo: if only 1 player in room, start immediately
+				room := ctx.Lobby.GetRoom(ctx.RoomCode)
+				if room != nil && len(room.Players) == 1 {
+					return s.startGame(ctx)
+				}
+			}
+		} else if isKey(key, "esc") || key.Type == tea.KeyEsc {
+			// Leave room — unready and go back to lobby
+			if ctx.Lobby != nil {
+				ctx.Lobby.SetPlayerReady(ctx.RoomCode, ctx.Fingerprint, false)
+				ctx.Lobby.LeaveRoom(ctx.RoomCode, ctx.Fingerprint)
+			}
+			ctx.RoomCode = ""
+			ls := NewLobbyScreen()
+			ls.refreshLobby(ctx)
+			return ls, nil
+		}
+	}
+	return s, nil
+}
+
+func (s *WaitingScreen) View(ctx *Context) string {
+	headerStyle := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("205")).
+		Bold(true)
+
+	readyStyle := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("46"))
+
+	notReadyStyle := lipgloss.NewStyle().
+		Foreground(lipgloss.Color("240"))
+
+	header := headerStyle.Render(fmt.Sprintf("── Waiting Room [%s] ──", ctx.RoomCode))
+
+	playerList := ""
+	if ctx.Lobby != nil {
+		room := ctx.Lobby.GetRoom(ctx.RoomCode)
+		if room != nil {
+			for _, p := range room.Players {
+				status := notReadyStyle.Render("...")
+				if p.Ready {
+					status = readyStyle.Render("READY")
+				}
+				cls := p.Class
+				if cls == "" {
+					cls = "?"
+				}
+				playerList += fmt.Sprintf("  %s (%s) %s\n", p.Name, cls, status)
+			}
+		}
+	}
+
+	menu := "[Enter] Ready"
+	if s.ready {
+		menu = "Waiting for other players..."
+	}
+	menu += "  [Esc] Leave"
+
+	return lipgloss.JoinVertical(lipgloss.Left,
+		header,
+		"",
+		playerList,
+		"",
+		menu,
+	)
+}