Drawbridges (down, up, automatic), frost spell and obsidian over cooled lava

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

src/traps.rs

@@ -485,7 +485,8 @@ impl Game {
             let near = |r: f32, ents: &Vec<Ent>| -> Vec<usize> { (0..ents.len()).filter(|&j| enemy(&ents[j]) && (ents[j].x - cx).powi(2) + (ents[j].y - cy).powi(2) < r * r).collect() };
             match t.kind {
                 TrapKind::Frost => {
-                    // always on: cold around it slows and bites
+                    // always on: cold around it slows and bites, and keeps lava next to it cooled
+                    self.cool_lava_around(cx, cy, 2.5, 3.0);
                     for j in near(2.5, &self.ents) {
                         self.ents[j].slow = self.ents[j].slow.max(0.5);
                         self.damage_unit(j, 2.0 * dt);