feat: add hard mode and weekly mutation system

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

config.yaml

@@ -42,3 +42,11 @@ backup:
   interval_min: 60
   # Directory for backup files
   dir: "./data/backup"
+
+difficulty:
+  # Monster stat multiplier in hard mode
+  hard_mode_monster_mult: 1.5
+  # Shop price multiplier in hard mode
+  hard_mode_shop_mult: 2.0
+  # Healing effectiveness multiplier in hard mode
+  hard_mode_heal_mult: 0.5

config/config.go

@@ -12,6 +12,13 @@ type Config struct {
 	Combat     CombatConfig     `yaml:"combat"`
 	Dungeon    DungeonConfig    `yaml:"dungeon"`
 	Backup     BackupConfig     `yaml:"backup"`
+	Difficulty DifficultyConfig `yaml:"difficulty"`
+}
+
+type DifficultyConfig struct {
+	HardModeMonsterMult float64 `yaml:"hard_mode_monster_mult"`
+	HardModeShopMult    float64 `yaml:"hard_mode_shop_mult"`
+	HardModeHealMult    float64 `yaml:"hard_mode_heal_mult"`
 }
 
 type ServerConfig struct {
@@ -56,6 +63,7 @@ func defaults() Config {
 		Combat: CombatConfig{FleeChance: 0.50, MonsterScaling: 1.15, SoloHPReduction: 0.50},
 		Dungeon: DungeonConfig{MapWidth: 60, MapHeight: 20, MinRooms: 5, MaxRooms: 8},
 		Backup:     BackupConfig{IntervalMin: 60, Dir: "./data/backup"},
+		Difficulty: DifficultyConfig{HardModeMonsterMult: 1.5, HardModeShopMult: 2.0, HardModeHealMult: 0.5},
 	}
 }
 

config/config_test.go

@@ -37,6 +37,15 @@ func TestLoadDefaults(t *testing.T) {
 	if cfg.Combat.MonsterScaling != 1.15 {
 		t.Errorf("expected monster scaling 1.15, got %f", cfg.Combat.MonsterScaling)
 	}
+	if cfg.Difficulty.HardModeMonsterMult != 1.5 {
+		t.Errorf("expected hard mode monster mult 1.5, got %f", cfg.Difficulty.HardModeMonsterMult)
+	}
+	if cfg.Difficulty.HardModeShopMult != 2.0 {
+		t.Errorf("expected hard mode shop mult 2.0, got %f", cfg.Difficulty.HardModeShopMult)
+	}
+	if cfg.Difficulty.HardModeHealMult != 0.5 {
+		t.Errorf("expected hard mode heal mult 0.5, got %f", cfg.Difficulty.HardModeHealMult)
+	}
 }
 
 func TestLoadFromFile(t *testing.T) {

game/mutation.go

@@ -0,0 +1,41 @@
+package game
+
+import (
+	"crypto/sha256"
+	"encoding/binary"
+	"fmt"
+	"time"
+
+	"github.com/tolelom/catacombs/config"
+)
+
+// Mutation represents a weekly gameplay modifier.
+type Mutation struct {
+	ID          string
+	Name        string
+	Description string
+	Apply       func(cfg *config.GameConfig)
+}
+
+// Mutations is the list of all available mutations.
+var Mutations = []Mutation{
+	{ID: "no_skills", Name: "Skill Lockout", Description: "Class skills are disabled",
+		Apply: func(cfg *config.GameConfig) { cfg.SkillUses = 0 }},
+	{ID: "speed_run", Name: "Speed Run", Description: "Turn timeout halved",
+		Apply: func(cfg *config.GameConfig) { cfg.TurnTimeoutSec = max(cfg.TurnTimeoutSec/2, 2) }},
+	{ID: "no_shop", Name: "Shop Closed", Description: "Shops are unavailable",
+		Apply: func(cfg *config.GameConfig) {}},
+	{ID: "glass_cannon", Name: "Glass Cannon", Description: "Double damage, half HP",
+		Apply: func(cfg *config.GameConfig) {}},
+	{ID: "elite_flood", Name: "Elite Flood", Description: "All monsters are elite",
+		Apply: func(cfg *config.GameConfig) {}},
+}
+
+// GetWeeklyMutation returns the mutation for the current week,
+// determined by a SHA-256 hash of the year and ISO week number.
+func GetWeeklyMutation() Mutation {
+	year, week := time.Now().ISOWeek()
+	h := sha256.Sum256([]byte(fmt.Sprintf("mutation:%d:%d", year, week)))
+	idx := int(binary.BigEndian.Uint64(h[:8]) % uint64(len(Mutations)))
+	return Mutations[idx]
+}

game/mutation_test.go

@@ -0,0 +1,68 @@
+package game
+
+import (
+	"testing"
+
+	"github.com/tolelom/catacombs/config"
+)
+
+func TestGetWeeklyMutation(t *testing.T) {
+	m := GetWeeklyMutation()
+	if m.ID == "" {
+		t.Error("expected non-empty mutation ID")
+	}
+	if m.Name == "" {
+		t.Error("expected non-empty mutation Name")
+	}
+	if m.Apply == nil {
+		t.Error("expected non-nil Apply function")
+	}
+	// Verify it returns one of the known mutations
+	found := false
+	for _, known := range Mutations {
+		if known.ID == m.ID {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Errorf("mutation ID %q not found in Mutations list", m.ID)
+	}
+}
+
+func TestMutationApplyNoSkills(t *testing.T) {
+	cfg := config.GameConfig{SkillUses: 3}
+	// Find the no_skills mutation
+	var m Mutation
+	for _, mut := range Mutations {
+		if mut.ID == "no_skills" {
+			m = mut
+			break
+		}
+	}
+	if m.ID == "" {
+		t.Fatal("no_skills mutation not found")
+	}
+	m.Apply(&cfg)
+	if cfg.SkillUses != 0 {
+		t.Errorf("expected SkillUses=0 after no_skills mutation, got %d", cfg.SkillUses)
+	}
+}
+
+func TestMutationApplySpeedRun(t *testing.T) {
+	cfg := config.GameConfig{TurnTimeoutSec: 10}
+	var m Mutation
+	for _, mut := range Mutations {
+		if mut.ID == "speed_run" {
+			m = mut
+			break
+		}
+	}
+	if m.ID == "" {
+		t.Fatal("speed_run mutation not found")
+	}
+	m.Apply(&cfg)
+	if cfg.TurnTimeoutSec != 5 {
+		t.Errorf("expected TurnTimeoutSec=5 after speed_run mutation, got %d", cfg.TurnTimeoutSec)
+	}
+}

game/session.go

@@ -82,6 +82,8 @@ type GameSession struct {
 	combatSignal   chan struct{}
 	done           chan struct{}
 	lastActivity   map[string]time.Time // fingerprint -> last activity time
+	HardMode       bool
+	ActiveMutation *Mutation
 }
 
 type playerActionMsg struct {

ui/lobby_view.go

@@ -32,6 +32,8 @@ type LobbyScreen struct {
 	joining      bool
 	codeInput    string
 	online       int
+	hardMode     bool
+	hardUnlocked bool
 }
 
 func NewLobbyScreen() *LobbyScreen {
@@ -62,6 +64,9 @@ func (s *LobbyScreen) refreshLobby(ctx *Context) {
 	}
 	s.online = len(ctx.Lobby.ListOnline())
 	s.cursor = 0
+	if ctx.Store != nil {
+		s.hardUnlocked = ctx.Store.IsUnlocked(ctx.Fingerprint, "hard_mode")
+	}
 }
 
 func (s *LobbyScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
@@ -115,6 +120,8 @@ func (s *LobbyScreen) Update(msg tea.Msg, ctx *Context) (Screen, tea.Cmd) {
 					return NewClassSelectScreen(), nil
 				}
 			}
+		} else if isKey(key, "h") && s.hardUnlocked {
+			s.hardMode = !s.hardMode
 		} else if isKey(key, "q") {
 			if ctx.Lobby != nil {
 				ctx.Lobby.PlayerOffline(ctx.Fingerprint)
@@ -135,6 +142,8 @@ func (s *LobbyScreen) View(ctx *Context) string {
 		joining:      s.joining,
 		codeInput:    s.codeInput,
 		online:       s.online,
+		hardMode:     s.hardMode,
+		hardUnlocked: s.hardUnlocked,
 	}
 	return renderLobby(state, ctx.Width, ctx.Height)
 }
@@ -148,6 +157,8 @@ type lobbyState struct {
 	joining      bool
 	codeInput    string
 	online       int
+	hardMode     bool
+	hardUnlocked bool
 }
 
 func renderLobby(state lobbyState, width, height int) string {
@@ -161,6 +172,13 @@ func renderLobby(state lobbyState, width, height int) string {
 
 	header := headerStyle.Render(fmt.Sprintf("── Lobby ── %d online ──", state.online))
 	menu := "[C] Create Room  [J] Join by Code  [Up/Down] Select  [Enter] Join  [Q] Back"
+	if state.hardUnlocked {
+		hardStatus := "OFF"
+		if state.hardMode {
+			hardStatus = "ON"
+		}
+		menu += fmt.Sprintf("  [H] Hard Mode: %s", hardStatus)
+	}
 
 	roomList := ""
 	for i, r := range state.rooms {