ESP: classify NPC damage immunity/armour/vulnerability

- Resolve server m_takedamage (DAMAGE_NO/DAMAGE_EVENTS_ONLY = immune).
- Classify gunship/strider/dropship as ARMORED (OnTakeDamage only accepts
  DMG_BLAST; only the RPG passes), and headcrab/antlion/manhack as VULN
  (gravity gun / physics impact).
- ESP draws ARMORED/VULN/IMMUNE tags above the name (new "Damage tags"
  toggle, [esp] dmg).
- Aimbot, silent aim, triggerbot and melee skip immune targets and armoured
  targets unless the active weapon is the RPG.

6 files changed, 118 insertions, 8 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index 2199be6..7f8b131 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -188,6 +188,24 @@ vocabulary / decisions.
   not aimbot targets and draw with the neutral colour. Lamarr
   (`models/Lamarr.mdl`) is additionally listed as neutral by model.
 
+## Damage classification
+
+- Every NPC is classified for ESP and target selection:
+  - `IMMUNE` — server `m_takedamage` is `DAMAGE_NO`/`DAMAGE_EVENTS_ONLY`.
+  - `ARMORED` — gunship, strider, dropship: their `OnTakeDamage` only accepts
+    blast damage (`DMG_BLAST`, with a damage threshold on gunships and a
+    distance check on striders). Only the RPG passes; bullets/grenades do not.
+  - `VULNERABLE` — headcrab, antlion, manhack: punting them with the gravity
+    gun / physics impact damage kills them.
+  - `NORMAL` — everything else.
+- ESP draws `ARMORED` (orange), `VULN` (cyan) or `IMMUNE` (grey) above the
+  name; toggle is `ESP → Damage tags` (`[esp] dmg=1`).
+- Aimbot/silent aim/triggerbot/melee skip `IMMUNE` targets always and
+  `ARMORED` targets unless the active weapon is the RPG
+  (`active_weapon_contains` for `rocket_launcher`/`rpg`).
+- Server `m_takedamage` (`FIELD_INTEGER`) is resolved alongside
+  `m_NPCState`; `0/1` means no damage.
+
 ## Bones / ESP
 
 - `SetupBones(BONE_USED_BY_ANYTHING)` with engine `Time()`; studio header via
diff --git a/src/esp.cpp b/src/esp.cpp
index 4a6b513..aa9f645 100644
--- a/src/esp.cpp
+++ b/src/esp.cpp
@@ -23,6 +23,7 @@ struct EspTarget {
   bool show_health;
   bool friendly;
   bool neutral;
+  int damage; // NpcDamageClass
   char name[48];
 };
 static EspTarget g_targets[128];
@@ -220,6 +221,48 @@ static bool npc_is_friendly(int idx, const char *model, int local_idx,
 }
 
 
+enum NpcDamageClass {
+  NPC_DMG_NORMAL = 0,
+  NPC_DMG_ARMORED,    // only blast damage (RPG) hurts it
+  NPC_DMG_VULNERABLE, // gravity gun / physics damage works well
+  NPC_DMG_IMMUNE      // m_takedamage says no damage at all
+};
+
+static bool model_has(const char *model, const char *needle) {
+  return model && strcasestr(model, needle) != nullptr;
+}
+
+// Server m_takedamage first (authoritative immunity), then the HL2 damage
+// rules for units whose OnTakeDamage filters specific damage types.
+static int npc_damage_class(int idx, const char *model) {
+  int td = server_npc_takedamage(idx);
+  if (td == 0 || td == 1) // DAMAGE_NO / DAMAGE_EVENTS_ONLY
+    return NPC_DMG_IMMUNE;
+  if (model_has(model, "gunship") || model_has(model, "combine_strider") ||
+      model_has(model, "dropship"))
+    return NPC_DMG_ARMORED;
+  if (model_has(model, "headcrab") || model_has(model, "antlion") ||
+      model_has(model, "manhack"))
+    return NPC_DMG_VULNERABLE;
+  return NPC_DMG_NORMAL;
+}
+
+static bool active_weapon_contains(void *local_ent, const char *needle);
+
+// Armoured units need blast damage; the RPG is the only stock weapon that
+// passes their OnTakeDamage filters. Immune units can never be damaged.
+static bool npc_can_be_damaged(int idx, const char *model) {
+  int dc = npc_damage_class(idx, model);
+  if (dc == NPC_DMG_IMMUNE)
+    return false;
+  if (dc != NPC_DMG_ARMORED)
+    return true;
+  int local = engine_get_local_player();
+  void *le = local > 0 ? entitylist_get(local) : nullptr;
+  return active_weapon_contains(le, "rocket_launcher") ||
+         active_weapon_contains(le, "rpg");
+}
+
 static void short_name(const char *model, char *out, size_t outn) {
   if (!model) { snprintf(out, outn, "NPC"); return; }
   const char *base = strrchr(model, '/');
@@ -334,6 +377,7 @@ static void esp_collect(int local_idx) {
     bool neutral = false;
     t.friendly = npc_is_friendly(idx, model, local_idx, neutral);
     t.neutral = neutral;
+    t.damage = npc_damage_class(idx, model);
     short_name(model, t.name, sizeof(t.name));
     if (npc && !model) snprintf(t.name, sizeof(t.name), "NPC");
   }
@@ -603,6 +647,8 @@ static bool select_aim_target(const QAngle &view, unsigned bone_mask,
     bool neutral = false;
     if (npc_is_friendly(idx, model, local, neutral) || neutral)
       return false;
+    if (!npc_can_be_damaged(idx, model))
+      return false;
     if (!bones_update(idx, ent))
       return false;
     Vector pts[32];
@@ -682,6 +728,8 @@ static bool select_aim_target(const QAngle &view, unsigned bone_mask,
     bool neutral = false;
     if (npc_is_friendly(idx, model, local, neutral) || neutral)
       continue;
+    if (!npc_can_be_damaged(idx, model))
+      continue;
 
     float maxz = g_net.maxs >= 0 ? *(float *)(e + g_net.maxs + 8) : 72.0f;
     if (!(maxz > 4.0f && maxz < 512.0f))
@@ -1063,6 +1111,8 @@ bool melee_aimbot_apply(CUserCmd *cmd) {
     bool neutral = false;
     if (npc_is_friendly(idx, model, local, neutral) || neutral)
       continue;
+    if (!npc_can_be_damaged(idx, model))
+      continue;
 
     Vector origin{*(float *)(e + g_net.origin),
                   *(float *)(e + g_net.origin + 4),
@@ -1394,6 +1444,8 @@ bool triggerbot_apply(CUserCmd *cmd) {
     bool neutral = false;
     if (npc_is_friendly(idx, model, local, neutral) || neutral)
       return false;
+    if (!npc_can_be_damaged(idx, model))
+      return false;
     cmd->buttons |= IN_ATTACK;
     static int logs = 0;
     if (logs < 5) {
@@ -1517,6 +1569,23 @@ void esp_draw() {
     }
     if (esp_option(ESP_OPT_SHOW_NAME))
       draw_text_col(left, top - 14, t.name, 255, 255, 255);
+    if (esp_option(ESP_OPT_DAMAGE_TAGS)) {
+      const char *tag = nullptr;
+      int tr = 255, tg = 255, tb = 255;
+      if (t.damage == NPC_DMG_ARMORED) {
+        tag = "ARMORED";
+        tr = 255; tg = 170; tb = 60;
+      } else if (t.damage == NPC_DMG_VULNERABLE) {
+        tag = "VULN";
+        tr = 90; tg = 220; tb = 255;
+      } else if (t.damage == NPC_DMG_IMMUNE) {
+        tag = "IMMUNE";
+        tr = 180; tg = 180; tb = 180;
+      }
+      if (tag)
+        draw_text_col(left, top - (esp_option(ESP_OPT_SHOW_NAME) ? 28 : 14),
+                      tag, tr, tg, tb);
+    }
   }
 
   // Groundwork probe: HL2H_BONE_DEBUG=1 draws a white marker at each NPC's
diff --git a/src/gui.cpp b/src/gui.cpp
index ebc1f62..b5fbc1d 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -359,12 +359,13 @@ static void build_cards() {
   static const char *esp_names[ESP_OPT_COUNT] = {
       "Show neutral",   "Show healthbar", "Show healthnum",
       "Show name",      "Show skeleton",  "Show box",
-      "Show speed graph"};
+      "Show speed graph", "Damage tags"};
   static const char *esp_descs[ESP_OPT_COUNT] = {
       "Include neutral wildlife.", "Draw a health bar.",
       "Draw the numeric health value.", "Draw the model name.",
       "Draw the animated bone links.", "Draw a bounding box.",
-      "Draw the lower-center speed graph."};
+      "Draw the lower-center speed graph.",
+      "Label ARMORED (needs blast/RPG) and VULN (gravity gun) units."};
   for (int i = 0; i < ESP_OPT_COUNT; i++)
     add_toggle(esp, esp_names[i], esp_descs[i], &g_esp_opt[i]);
 
diff --git a/src/hl2h.h b/src/hl2h.h
index 3ccf7b5..287563c 100644
--- a/src/hl2h.h
+++ b/src/hl2h.h
@@ -192,7 +192,8 @@ enum EspOption {
   ESP_OPT_SHOW_SKELETON = 4,
   ESP_OPT_SHOW_BOX = 5,
   ESP_OPT_SHOW_SPEEDGRAPH = 6,
-  ESP_OPT_COUNT = 7
+  ESP_OPT_DAMAGE_TAGS = 7,
+  ESP_OPT_COUNT = 8
 };
 enum AimBone {
   AIM_BONE_HEAD = 0,
@@ -273,6 +274,7 @@ int server_active_weapon(int idx);
 int server_npc_relation(int idx, int local_idx);
 bool server_npc_has_follow_target(int idx);
 int server_npc_state(int idx);
+int server_npc_takedamage(int idx);
 int server_npc_turret_flags(int idx);
 int server_model_index(void *base);
 void find_modules();
diff --git a/src/menu.cpp b/src/menu.cpp
index 0ce6c05..eb1075a 100644
--- a/src/menu.cpp
+++ b/src/menu.cpp
@@ -78,7 +78,8 @@ bool g_aim_fov_circle = true;
 int g_silent_fov = 60;
 
 // ESP sub-options. Defaults match the pre-option behaviour: everything on.
-bool g_esp_opt[ESP_OPT_COUNT] = {true, true, true, true, true, true, true};
+bool g_esp_opt[ESP_OPT_COUNT] = {true, true, true, true, true, true, true,
+                                 true};
 
 // ---------------------------------------------------------------------------
 // config persistence (INI format)
@@ -221,12 +222,14 @@ void config_save() {
           (int)g_item_ammo, (int)g_item_armor, (int)g_item_weapons,
           (int)g_item_crates, (int)g_item_distance, g_item_max_dist);
   fprintf(f, "[esp]\nactive=%d\nbind=%d\nneutral=%d\nhealthbar=%d\n"
-             "healthnum=%d\nname=%d\nskeleton=%d\nbox=%d\nspeedgraph=%d\n",
+             "healthnum=%d\nname=%d\nskeleton=%d\nbox=%d\nspeedgraph=%d\n"
+             "dmg=%d\n",
           g_esp.active, g_esp.bind, g_esp_opt[ESP_OPT_SHOW_NEUTRAL],
           g_esp_opt[ESP_OPT_SHOW_HEALTHBAR],
           g_esp_opt[ESP_OPT_SHOW_HEALTHNUM], g_esp_opt[ESP_OPT_SHOW_NAME],
           g_esp_opt[ESP_OPT_SHOW_SKELETON], g_esp_opt[ESP_OPT_SHOW_BOX],
-          g_esp_opt[ESP_OPT_SHOW_SPEEDGRAPH]);
+          g_esp_opt[ESP_OPT_SHOW_SPEEDGRAPH],
+          g_esp_opt[ESP_OPT_DAMAGE_TAGS]);
   gui_config_write(f);
   bool ok = ferror(f) == 0;
   if (fflush(f) != 0)
@@ -427,6 +430,8 @@ static bool config_load() {
           g_esp_opt[ESP_OPT_SHOW_BOX] = atoi(val) != 0;
         else if (strcmp(key, "speedgraph") == 0)
           g_esp_opt[ESP_OPT_SHOW_SPEEDGRAPH] = atoi(val) != 0;
+        else if (strcmp(key, "dmg") == 0)
+          g_esp_opt[ESP_OPT_DAMAGE_TAGS] = atoi(val) != 0;
       }
       if (strcmp(key, "active") == 0)
         cur->active = atoi(val) != 0;
diff --git a/src/server.cpp b/src/server.cpp
index c2864c8..e9fd921 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -51,6 +51,7 @@ static int g_srv_followtarget = -1;
 static int g_srv_spawnflags = -1;
 static int g_srv_hacked = -1;
 static int g_srv_npcstate = -1;
+static int g_srv_takedamage = -1;
 static bool g_srv_ready = false;
 static bool g_srv_checked = false;
 
@@ -141,15 +142,17 @@ bool resolve_server_netvars() {
   g_srv_spawnflags = datamap_offset("m_spawnflags", FIELD_INTEGER, 0x4);
   g_srv_hacked = datamap_offset("m_bHackedByAlyx", FIELD_BOOLEAN);
   g_srv_npcstate = datamap_offset("m_NPCState", FIELD_INTEGER);
+  g_srv_takedamage = datamap_offset("m_takedamage", FIELD_INTEGER);
   g_srv_ready = g_srv_health > 0;
   if (g_srv_ready) {
     logf("server datamap (%s): health=%d maxhealth=%d lifeste=%d "
          "modelindex=%d absvel=%d vel=%d activeweapon=%d relationship=%d "
-         "followtarget=%d spawnflags=%d hacked=%d npcstate=%d",
+         "followtarget=%d spawnflags=%d hacked=%d npcstate=%d "
+         "takedamage=%d",
          g_server.path.c_str(), g_srv_health, g_srv_maxhealth, g_srv_lifestate,
          g_srv_modelindex, g_srv_absvelocity, g_srv_velocity,
          g_srv_activeweapon, g_srv_relationship, g_srv_followtarget,
-         g_srv_spawnflags, g_srv_hacked, g_srv_npcstate);
+         g_srv_spawnflags, g_srv_hacked, g_srv_npcstate, g_srv_takedamage);
     fail_logged = false;
   } else if (!fail_logged) {
     fail_logged = true;
@@ -268,6 +271,18 @@ int server_npc_state(int idx) {
   return *(int *)((uintptr_t)base + g_srv_npcstate);
 }
 
+// TAKEDAMAGE: 0 = DAMAGE_NO, 1 = DAMAGE_EVENTS_ONLY, 2 = DAMAGE_YES,
+// 3 = DAMAGE_AIM. 0/1 cannot be damaged at all.
+int server_npc_takedamage(int idx) {
+  if (!g_srv_ready || g_srv_takedamage < 0)
+    return -1;
+  void *base = nullptr;
+  server_entity_health(idx, nullptr, nullptr, &base);
+  if (!base)
+    return -1;
+  return *(int *)((uintptr_t)base + g_srv_takedamage);
+}
+
 bool server_npc_has_follow_target(int idx) {
   if (!g_srv_ready || g_srv_followtarget < 0)
     return false;