Add Iron Coast II Black Tide eight-mission campaign

mods/iron_coast_depth_charge/scripts/weapon.rhai

@@ -0,0 +1,48 @@
+// Damage is collision-triggered. Empty space, aircraft and inactive equipment
+// never start a blast. Native targeting handles the primary ground collision.
+fn on_fire(event, state, random) {
+    if event.hostile { return #{commands: [], state: state}; }
+    let shots = if state.contains("shots") { state.shots % 100000 + 1 } else { 1 };
+    let hits = if state.contains("hits") { state.hits } else { 0 };
+    #{commands: [#{op: "play_sound", sound: "iron_coast_depth_charge:fire"}],
+      state: #{shots: shots, hits: hits}}
+}
+
+fn on_hit(event, state, random) {
+    let shots = if state.contains("shots") { state.shots } else { 0 };
+    let hits = if state.contains("hits") { state.hits % 100000 + 1 } else { 1 };
+    let center_x = event.x;
+    let center_y = event.y;
+    for enemy in event.entities {
+        if enemy.entity == event.entity {
+            center_x = enemy.x + enemy.width / 2;
+            center_y = enemy.y + enemy.height / 2;
+        }
+    }
+    let commands = [#{op: "play_sound", sound: "iron_coast_depth_charge:impact"},
+                    #{op: "effect", kind: "ground_blast", x: center_x, y: center_y}];
+    let struck = [event.entity];
+    for neighbor in 0..3 {
+        let chosen = #{};
+        let nearest = 1000000;
+        for enemy in event.entities {
+            let cx = enemy.x + enemy.width / 2;
+            let cy = enemy.y + enemy.height / 2;
+            if !enemy.ground || enemy.health <= 0 || struck.contains(enemy.entity)
+                || cx < 0 || cx >= 320 || cy < 0 || cy >= 200 { continue; }
+            let dx = cx - center_x;
+            let dy = cy - center_y;
+            let distance = dx * dx + dy * dy;
+            if distance <= 36 * 36 && distance < nearest {
+                chosen = #{entity: enemy.entity};
+                nearest = distance;
+            }
+        }
+        if !chosen.contains("entity") { break; }
+        let damage = if nearest <= 16 * 16 { 36 } else { 20 };
+        commands.push(#{op: "damage", entity: chosen.entity, amount: damage});
+        struck.push(chosen.entity);
+        hits = hits % 100000 + 1;
+    }
+    #{commands: commands, state: #{shots: shots, hits: hits}}
+}