Can now open secret walls and pick up machine gun

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

lib/features/entities/entity.dart

@@ -27,4 +27,40 @@ abstract class Entity<T> {
   }
 
   Coordinate2D get position => Coordinate2D(x, y);
+
+  // NEW: Checks if a projectile or sightline from 'source' can reach this entity
+  bool hasLineOfSightFrom(
+    Coordinate2D source,
+    double sourceAngle,
+    double distance,
+    bool Function(int x, int y) isWalkable,
+  ) {
+    // Corrected Integer Bresenham Algorithm
+    int currentX = source.x.toInt();
+    int currentY = source.y.toInt();
+    int targetX = x.toInt();
+    int targetY = y.toInt();
+
+    int dx = (targetX - currentX).abs();
+    int dy = -(targetY - currentY).abs();
+    int sx = currentX < targetX ? 1 : -1;
+    int sy = currentY < targetY ? 1 : -1;
+    int err = dx + dy;
+
+    while (true) {
+      if (!isWalkable(currentX, currentY)) return false;
+      if (currentX == targetX && currentY == targetY) break;
+
+      int e2 = 2 * err;
+      if (e2 >= dy) {
+        err += dy;
+        currentX += sx;
+      }
+      if (e2 <= dx) {
+        err += dx;
+        currentY += sy;
+      }
+    }
+    return true;
+  }
 }