feat(conditions): add blinded/invisible/helpless/fascinated combat rules

src/pf1e_simulator/combat.py

@@ -158,6 +158,9 @@ _DELAY_INITIATIVE_STEP = 0.5  # PF1e: a delay slots 0.5 below its anchor total
 _TOTAL_DEFENSE_AC_BONUS = 4  # PF1e: total defense grants +4 dodge AC
 _FIGHT_DEFENSIVELY_AC_BONUS = 2  # PF1e: fighting defensively grants +2 dodge AC
 _FIGHT_DEFENSIVELY_ATTACK_PENALTY = -4  # PF1e: and -4 on attacks / crit confirms
+_TOTAL_CONCEALMENT_PCT = 50  # PF1e: a blinded attacker's targets have total concealment
+_INVISIBLE_ATTACK_BONUS = 2  # PF1e: +2 attack rolls for an invisible attacker
+_HELPLESS_MELEE_BONUS = 4  # PF1e: +4 melee attack rolls (and crit confirms) vs helpless
 _AID_ANOTHER_DC = 10  # PF1e: aid another is an attack roll against AC 10
 _AID_ANOTHER_BONUS = 2  # PF1e: a successful aid grants +2 (next attack or AC)
 _RUN_SPEED_FACTOR = 4  # PF1e: running is a full-round action at 4x speed
@@ -1806,6 +1809,13 @@ class CombatEngine:
         )
         if self._is_ranged_attack(weapon) and self._has_condition_named(attacker, "prone"):
             atk_mods.append(StatModifier(target="attack", value=-4))
+        # PF1e: an invisible attacker strikes from an unknown direction (+2 on
+        # attack and crit confirmation, target loses its Dex bonus to AC).
+        if self._has_condition_named(attacker, "invisible"):
+            atk_mods.append(StatModifier(target="attack", value=_INVISIBLE_ATTACK_BONUS))
+        # PF1e: melee attacks against a helpless target gain +4 (ranged none).
+        if weapon.kind == "melee" and self._has_condition_named(target, "helpless"):
+            atk_mods.append(StatModifier(target="attack", value=_HELPLESS_MELEE_BONUS))
         attack_mod = resolve_modifiers(atk_mods)
         pa_amt = self._power_attack_amt(attacker) if weapon.kind == "melee" else 0
         fd_penalty = (
@@ -1816,8 +1826,13 @@ class CombatEngine:
             + fim_penalty + fd_penalty + attacker.aid_attack_bonus
         )
         # Check if target denies DEX to AC (flat-footed); a running target
-        # loses its DEX bonus too (U5e), reusing the same AC path.
-        denies_dex = self.has_condition_flag(target, "denies_dex_to_ac") or target.running
+        # loses its DEX bonus too (U5e), reusing the same AC path. An
+        # invisible attacker also denies the target's DEX bonus to AC.
+        denies_dex = (
+            self.has_condition_flag(target, "denies_dex_to_ac")
+            or target.running
+            or self._has_condition_named(attacker, "invisible")
+        )
         full_ac_base = (
             target.combatant.ac.flat_footed
             if denies_dex
@@ -1918,13 +1933,20 @@ class CombatEngine:
             )
             crit = confirm != _NATURAL_ONE and confirm_total >= ac
         concealment = self._concealment_chance(target)
-        if concealment > 0:
+        # PF1e: a blinded character's opponents count as having total
+        # concealment against it — the blinded attacker itself misses 50%.
+        attacker_blinded = self._has_condition_named(attacker, "blinded")
+        miss_chance = (
+            max(concealment, _TOTAL_CONCEALMENT_PCT) if attacker_blinded else concealment
+        )
+        if miss_chance > 0:
             pct = self._rng.d100()
-            missed = pct <= concealment
+            missed = pct <= miss_chance
+            source = "attacker blinded" if attacker_blinded else "concealment"
             self._log(
                 f"round {self._current_round} {attacker.combatant.id}: "
-                f"concealment vs {target.combatant.id}: "
-                f"d100({pct}) {'<=' if missed else '>'} {concealment}% "
+                f"{source} vs {target.combatant.id}: "
+                f"d100({pct}) {'<=' if missed else '>'} {miss_chance}% "
                 f"— attack {'misses' if missed else 'lands'}"
             )
             if missed:

src/pf1e_simulator/conditions.py

@@ -217,6 +217,20 @@ ASLEEP = Condition(
 )
 
 
+# Helpless: helpless for all intents, treated as Dex 0 (loses Dex to AC),
+# can't act; melee attackers gain +4 (engine logic in resolve_attack) (CRB)
+HELPLESS = Condition(
+    name="helpless",
+    denies_dex_to_ac=True,
+    cant_act=True,
+)
+
+# Fascinated: distracted, takes no actions other than paying attention (CRB)
+FASCINATED = Condition(
+    name="fascinated",
+    cant_act=True,
+)
+
 # Grappled: -4 Dex, -2 attack, no movement, no AoO, can't cast without concentration (CRB)
 GRAPPLED = Condition(
     name="grappled",
@@ -267,6 +281,13 @@ DISPLACED = Condition(
     miss_chance=50,
 )
 
+# Invisible: total concealment against attacks targeting it; the attacker-side
+# +2 on attack rolls and the target's lost Dex bonus are engine logic (CRB)
+INVISIBLE = Condition(
+    name="invisible",
+    miss_chance=50,
+)
+
 # ── Registry ─────────────────────────────────────────────────────────────────
 CONDITIONS_BY_NAME: dict[str, Condition] = {
     c.name: c
@@ -275,5 +296,6 @@ CONDITIONS_BY_NAME: dict[str, Condition] = {
         BLINDED, DEAFENED, FLAT_FOOTED, PRONE, STUNNED, PARALYZED,
         NAUSEATED, DAZED, STAGGERED, FRIGHTENED, PANICKED, COWERING,
         ASLEEP, GRAPPLED, PINNED, BLURRED, DISPLACED,
+        HELPLESS, FASCINATED, INVISIBLE,
     ]
 }