3 files changed, 97 insertions, 13 deletions

diff --git a/internal/combat/formulas.go b/internal/combat/formulas.go
index f4e1ba2..f165923 100644
--- a/internal/combat/formulas.go
+++ b/internal/combat/formulas.go
@@ -2,8 +2,24 @@ package combat
 
 import "math/rand"
 
-func EffectiveRoll(level int, styleBonus int, equipBonus int) int {
-	effective := level + styleBonus + 8
+func PlayerEffective(level, styleBonus int) int {
+	return level + styleBonus + 8
+}
+
+func NPCEffective(level int) int {
+	return level + 9
+}
+
+// ScienceEffective is the effective-level formula for science attacks. It is
+// intentionally the same as NPCEffective (level + 9) and is applied to BOTH the
+// attacker and defender of a science-mod exchange (see scienceAttack), giving a
+// symmetric science-vs-science model with no attack styles. It is kept as a
+// distinct function to document that intent independently of NPCEffective.
+func ScienceEffective(level int) int {
+	return level + 9
+}
+
+func AttackRoll(effective, equipBonus int) int {
 	return effective * (equipBonus + 64)
 }
 
@@ -17,13 +33,11 @@ func HitChance(attackRoll, defenseRoll int) float64 {
 }
 
 func HitCheck(attackRoll, defenseRoll int) bool {
-	chance := HitChance(attackRoll, defenseRoll)
-	return rand.Float64() < chance
+	return rand.Float64() < HitChance(attackRoll, defenseRoll)
 }
 
-func MaxHit(level int, styleBonus int, equipBonus int) int {
-	effective := level + styleBonus + 8
-	hit := (effective * (equipBonus + 64)) / 512
+func MaxHit(effective, equipStrBonus int) int {
+	hit := (effective*(equipStrBonus+64) + 320) / 640
 	if hit < 1 {
 		hit = 1
 	}
@@ -34,7 +48,11 @@ func RollDamage(maxHit int) int {
 	if maxHit <= 0 {
 		return 0
 	}
-	return 1 + rand.Intn(maxHit)
+	d := rand.Intn(maxHit + 1)
+	if d < 1 {
+		d = 1
+	}
+	return d
 }
 
 func AttackStyleBonus(style string) (attack, strength, defense int) {
@@ -69,15 +87,15 @@ func RangedStyleBonus(style string) (ranged, defense int) {
 
 func SelectBonus(attackType string, stab, slash, crush, science, ranged int) int {
 	switch attackType {
-	case "stab":
+	case AttackStab:
 		return stab
-	case "slash":
+	case AttackSlash:
 		return slash
-	case "crush":
+	case AttackCrush:
 		return crush
-	case "science":
+	case AttackScience:
 		return science
-	case "ranged":
+	case AttackRanged:
 		return ranged
 	default:
 		return crush
diff --git a/internal/combat/types.go b/internal/combat/types.go
new file mode 100644
index 0000000..bb2a897
--- /dev/null
+++ b/internal/combat/types.go
@@ -0,0 +1,36 @@
+package combat
+
+// Attack type identifiers shared across combat, mobs, weapons, hazards and
+// validation. These are the canonical string values stored in YAML.
+const (
+	AttackStab    = "stab"
+	AttackSlash   = "slash"
+	AttackCrush   = "crush"
+	AttackRanged  = "ranged"
+	AttackScience = "science"
+
+	// DefaultAttackType is the fallback when no attack type is specified.
+	DefaultAttackType = AttackCrush
+)
+
+// MeleeAttackTypes lists the melee attack types (exactly one of which a mob
+// must have).
+var MeleeAttackTypes = []string{AttackStab, AttackSlash, AttackCrush}
+
+// AllAttackTypes lists every valid attack type.
+var AllAttackTypes = []string{AttackStab, AttackSlash, AttackCrush, AttackRanged, AttackScience}
+
+// IsMeleeType reports whether t is a melee attack type.
+func IsMeleeType(t string) bool {
+	return t == AttackStab || t == AttackSlash || t == AttackCrush
+}
+
+// IsValidAttackType reports whether t is any recognized attack type.
+func IsValidAttackType(t string) bool {
+	switch t {
+	case AttackStab, AttackSlash, AttackCrush, AttackRanged, AttackScience:
+		return true
+	default:
+		return false
+	}
+}
diff --git a/internal/combat/types_test.go b/internal/combat/types_test.go
new file mode 100644
index 0000000..a999eb6
--- /dev/null
+++ b/internal/combat/types_test.go
@@ -0,0 +1,30 @@
+package combat
+
+import "testing"
+
+func TestIsMeleeType(t *testing.T) {
+	melee := []string{AttackStab, AttackSlash, AttackCrush}
+	for _, m := range melee {
+		if !IsMeleeType(m) {
+			t.Errorf("IsMeleeType(%q) = false, want true", m)
+		}
+	}
+	for _, nm := range []string{AttackRanged, AttackScience, "", "magic"} {
+		if IsMeleeType(nm) {
+			t.Errorf("IsMeleeType(%q) = true, want false", nm)
+		}
+	}
+}
+
+func TestIsValidAttackType(t *testing.T) {
+	for _, v := range AllAttackTypes {
+		if !IsValidAttackType(v) {
+			t.Errorf("IsValidAttackType(%q) = false, want true", v)
+		}
+	}
+	for _, iv := range []string{"", "magic", "melee"} {
+		if IsValidAttackType(iv) {
+			t.Errorf("IsValidAttackType(%q) = true, want false", iv)
+		}
+	}
+}