Add crawling score, applied to prone movement cost

data/json/body_parts.json

@@ -135,7 +135,7 @@
     "hit_size": 13,
     "hit_difficulty": 0.95,
     "limb_type": "arm",
-    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "lift", 0.5 ], [ "balance", 0.15 ], [ "block", 1.0 ], [ "swim", 0.1 ] ],
+    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "lift", 0.5 ], [ "balance", 0.15 ], [ "block", 1.0 ], [ "swim", 0.1 ], [ "crawl", 0.3 ] ],
     "side": "left",
     "legacy_id": "ARM_L",
     "hot_morale_mod": 0.5,
@@ -167,7 +167,7 @@
     "hit_size": 13,
     "hit_difficulty": 0.95,
     "limb_type": "arm",
-    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "lift", 0.5 ], [ "balance", 0.15 ], [ "block", 1.0 ], [ "swim", 0.1 ] ],
+    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "lift", 0.5 ], [ "balance", 0.15 ], [ "block", 1.0 ], [ "swim", 0.1 ], [ "crawl", 0.3 ] ],
     "side": "right",
     "legacy_id": "ARM_R",
     "hot_morale_mod": 0.5,
@@ -255,7 +255,7 @@
     "hit_size": 13,
     "hit_difficulty": 0.9,
     "limb_type": "leg",
-    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "move_speed", 0.5 ], [ "swim", 0.15 ], [ "block", 1 ] ],
+    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "move_speed", 0.5 ], [ "swim", 0.15 ], [ "block", 1 ], [ "crawl", 0.2 ] ],
     "encumb_impacts_dodge": true,
     "side": "left",
     "legacy_id": "LEG_L",
@@ -290,7 +290,7 @@
     "hit_size": 13,
     "hit_difficulty": 0.9,
     "limb_type": "leg",
-    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "move_speed", 0.5 ], [ "swim", 0.15 ], [ "block", 1 ] ],
+    "limb_scores": [ [ "manip", 0.1, 0.2 ], [ "move_speed", 0.5 ], [ "swim", 0.15 ], [ "block", 1 ], [ "crawl", 0.2 ] ],
     "encumb_impacts_dodge": true,
     "side": "right",
     "legacy_id": "LEG_R",

data/json/character_modifiers.json

@@ -83,6 +83,13 @@
     "mod_type": "x",
     "value": { "limb_score": "breathing" }
   },
+  {
+    "type": "character_mod",
+    "id": "crawl_speed_movecost_mod",
+    "description": "Crawl speed movecost modifier",
+    "mod_type": "x",
+    "value": { "limb_score": "crawl", "nominator": 1.2 }
+  },
   {
     "type": "character_mod",
     "id": "limb_speed_movecost_mod",

data/json/limb_scores.json

@@ -83,5 +83,12 @@
     "name": "Swimming",
     "affected_by_wounds": true,
     "affected_by_encumb": true
+  },
+  {
+    "type": "limb_score",
+    "id": "crawl",
+    "name": "Crawling",
+    "affected_by_wounds": true,
+    "affected_by_encumb": true
   }
 ]

src/character.cpp

@@ -169,6 +169,8 @@ static const bionic_id bio_voice( "bio_voice" );
 static const character_modifier_id character_modifier_aim_speed_dex_mod( "aim_speed_dex_mod" );
 static const character_modifier_id character_modifier_aim_speed_mod( "aim_speed_mod" );
 static const character_modifier_id character_modifier_aim_speed_skill_mod( "aim_speed_skill_mod" );
+static const character_modifier_id
+character_modifier_crawl_speed_movecost_mod( "crawl_speed_movecost_mod" );
 static const character_modifier_id character_modifier_limb_run_cost_mod( "limb_run_cost_mod" );
 static const character_modifier_id
 character_modifier_limb_speed_movecost_mod( "limb_speed_movecost_mod" );
@@ -8907,7 +8909,8 @@ int Character::run_cost( int base_cost, bool diag ) const
             }
         }
 
-        movecost *= get_modifier( character_modifier_limb_run_cost_mod );
+        movecost *= get_modifier( is_prone() ? character_modifier_crawl_speed_movecost_mod :
+                                  character_modifier_limb_run_cost_mod );
 
         movecost *= mutation_value( "movecost_modifier" );
         if( flatground ) {
@@ -8969,7 +8972,7 @@ int Character::run_cost( int base_cost, bool diag ) const
         movecost /= get_modifier( character_modifier_stamina_move_cost_mod );
 
         if( !is_mounted() && !is_prone() && has_effect( effect_downed ) ) {
-            movecost *= 3;
+            movecost *= get_modifier( character_modifier_crawl_speed_movecost_mod ) * 2;
         }
     }