feat: add combo skill system with 5 combos

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

combat/combo.go

@@ -0,0 +1,91 @@
+package combat
+
+import "github.com/tolelom/catacombs/entity"
+
+type ComboAction struct {
+	Class      entity.Class
+	ActionType string // "attack", "skill", "item"
+}
+
+type ComboEffect struct {
+	DamageMultiplier float64 // multiplied onto each AttackIntent.Multiplier
+	BonusDamage      int     // added to each AttackIntent.PlayerATK
+	HealAll          int     // heal all players after resolution
+	Message          string  // shown in combat log
+}
+
+type ComboDef struct {
+	Name     string
+	Required []ComboAction
+	Effect   ComboEffect
+}
+
+var comboDefs = []ComboDef{
+	{
+		Name: "Ice Shatter",
+		Required: []ComboAction{
+			{Class: entity.ClassMage, ActionType: "skill"},
+			{Class: entity.ClassWarrior, ActionType: "attack"},
+		},
+		Effect: ComboEffect{DamageMultiplier: 1.5, Message: "💥 ICE SHATTER! Frozen enemies shatter!"},
+	},
+	{
+		Name: "Holy Assault",
+		Required: []ComboAction{
+			{Class: entity.ClassHealer, ActionType: "skill"},
+			{Class: entity.ClassWarrior, ActionType: "attack"},
+		},
+		Effect: ComboEffect{DamageMultiplier: 1.3, HealAll: 10, Message: "✨ HOLY ASSAULT! Blessed strikes heal the party!"},
+	},
+	{
+		Name: "Shadow Strike",
+		Required: []ComboAction{
+			{Class: entity.ClassRogue, ActionType: "skill"},
+			{Class: entity.ClassMage, ActionType: "attack"},
+		},
+		Effect: ComboEffect{DamageMultiplier: 1.4, Message: "🗡️ SHADOW STRIKE! Magical shadows amplify the attack!"},
+	},
+	{
+		Name: "Full Assault",
+		Required: []ComboAction{
+			{Class: entity.ClassWarrior, ActionType: "attack"},
+			{Class: entity.ClassMage, ActionType: "attack"},
+			{Class: entity.ClassRogue, ActionType: "attack"},
+		},
+		Effect: ComboEffect{DamageMultiplier: 1.3, BonusDamage: 5, Message: "⚔️ FULL ASSAULT! Combined attack overwhelms!"},
+	},
+	{
+		Name: "Restoration",
+		Required: []ComboAction{
+			{Class: entity.ClassHealer, ActionType: "skill"},
+			{Class: entity.ClassRogue, ActionType: "item"},
+		},
+		Effect: ComboEffect{HealAll: 20, Message: "💚 RESTORATION! Combined healing surges!"},
+	},
+}
+
+func DetectCombos(actions map[string]ComboAction) []ComboDef {
+	var triggered []ComboDef
+	for _, combo := range comboDefs {
+		if matchesCombo(combo.Required, actions) {
+			triggered = append(triggered, combo)
+		}
+	}
+	return triggered
+}
+
+func matchesCombo(required []ComboAction, actions map[string]ComboAction) bool {
+	for _, req := range required {
+		found := false
+		for _, act := range actions {
+			if act.Class == req.Class && act.ActionType == req.ActionType {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+	return true
+}

combat/combo_test.go

@@ -0,0 +1,45 @@
+package combat
+
+import (
+	"testing"
+
+	"github.com/tolelom/catacombs/entity"
+)
+
+func TestDetectCombo_IceShatter(t *testing.T) {
+	actions := map[string]ComboAction{
+		"mage":    {Class: entity.ClassMage, ActionType: "skill"},
+		"warrior": {Class: entity.ClassWarrior, ActionType: "attack"},
+	}
+	combos := DetectCombos(actions)
+	if len(combos) == 0 {
+		t.Fatal("expected Ice Shatter combo")
+	}
+	if combos[0].Name != "Ice Shatter" {
+		t.Errorf("expected 'Ice Shatter', got %q", combos[0].Name)
+	}
+}
+
+func TestDetectCombo_NoMatch(t *testing.T) {
+	actions := map[string]ComboAction{
+		"w1": {Class: entity.ClassWarrior, ActionType: "attack"},
+		"w2": {Class: entity.ClassWarrior, ActionType: "attack"},
+	}
+	combos := DetectCombos(actions)
+	if len(combos) != 0 {
+		t.Errorf("expected no combos, got %d", len(combos))
+	}
+}
+
+func TestDetectCombo_Multiple(t *testing.T) {
+	// Healer skill + Warrior attack + Rogue item → Holy Assault + Restoration
+	actions := map[string]ComboAction{
+		"healer":  {Class: entity.ClassHealer, ActionType: "skill"},
+		"warrior": {Class: entity.ClassWarrior, ActionType: "attack"},
+		"rogue":   {Class: entity.ClassRogue, ActionType: "item"},
+	}
+	combos := DetectCombos(actions)
+	if len(combos) != 2 {
+		t.Errorf("expected 2 combos, got %d", len(combos))
+	}
+}