Title demo: the knights come from a forest above ground; lighter meadow, darker trees, no lava above ground

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

src/surface.rs

@@ -64,6 +64,14 @@ impl Game {
                     continue;
                 }
                 self.map.set_sky(i, true);
+                // no lava under the open sky: rivers up here carry water
+                let tl = &mut self.map.t[i];
+                match tl.kind {
+                    Kind::Lava | Kind::Obsidian => tl.kind = Kind::Water,
+                    Kind::LavaBridge => tl.kind = Kind::Bridge,
+                    Kind::Drawbridge => tl.res &= !DB_LAVA,
+                    _ => {}
+                }
                 if keep {
                     continue;
                 }
@@ -195,4 +203,22 @@ mod tests {
         // the heroes find their way from the gate to the core
         assert!(g.map.hero_path_to_core(idx(gx + 1, gy + 1)).is_some());
     }
+
+    #[test]
+    fn no_lava_under_the_open_sky() {
+        let mut g = Game::new(31, 128, 96);
+        // a lava river across the whole map
+        for x in 2..126 {
+            for y in 40..44 {
+                g.map.t[idx(x, y)].kind = Kind::Lava;
+            }
+        }
+        g.add_surface(31, 0.5, 3);
+        for i in 0..g.map.t.len() {
+            if g.map.sky(i) {
+                assert!(!matches!(g.map.t[i].kind, Kind::Lava | Kind::LavaBridge), "lava above ground");
+            }
+        }
+        assert!(g.map.t.iter().any(|t| t.kind == Kind::Lava), "the lava below stays");
+    }
 }