Surface world: grass in daylight, forests, cliffs with cave mouths; free-game and editor option

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/campaign.rs

@@ -48,6 +48,7 @@ pub struct MissionDef {
     pub rivals: Vec<(f32, f32, u8, u8)>, // rival masters: position (fraction of the map), difficulty, side (2 Mossgrim, 3 Lady Nightwell)
     pub islands: Vec<IslandDef>,
     pub caves: Vec<CaveDef>,
+    pub surface: f32, // share of the width from where the map lies above ground (0: none)
 }
 
 // an island in a lake of water or lava, with treasure and/or a mana spring
@@ -166,6 +167,7 @@ fn base(key: &str, size: (usize, usize), seed: u32, goals: Vec<Goal>) -> Mission
         rivals: Vec::new(),
         islands: Vec::new(),
         caves: Vec::new(),
+        surface: 0.0,
     }
 }
 
@@ -181,6 +183,7 @@ pub fn mission_def_from_doc(d: &crate::campaign_doc::MissionDoc) -> MissionDef {
     out.gate = d.waves;
     out.gate_defenders = d.waves;
     out.time_limit = d.time_limit;
+    out.surface = if d.gen.surface { 0.5 } else { 0.0 };
     out
 }
 
@@ -537,6 +540,9 @@ fn start_mission_def(d: &MissionDef, i: usize, carry: Option<&Carry>, coop: bool
     }
     g.place_dwarf_caves(d.seed);
     g.add_wilds(d.seed, false);
+    if d.surface > 0.0 {
+        g.add_surface(d.seed, d.surface, 2 + (h / 64) as u32);
+    }
     g.init_research(Some(i));
     g.init_fog();
     let heart = d.gate || d.forts.iter().any(|f| f.heart);