Implement enemy AI and handler; add placeable radar object; enhance maze functionality

utils/utils.rb

@@ -9,4 +9,34 @@ def intersects?(rect1, rect2)
   return false if y1 >= y2 + h2   # rect1 is below rect2
 
   true  # overlap exists
+end
+
+def line_of_sight?(x1, y1, x2, y2, rect)
+  rx, ry, rw, rh = rect
+  rx, ry, rw, rh = rx - 2, ry - 2, rw + 4, rh + 4
+
+  # The 4 edges of the rect as line segments
+  edges = [
+    [rx,      ry,      rx + rw, ry     ],  # top
+    [rx,      ry + rh, rx + rw, ry + rh],  # bottom
+    [rx,      ry,      rx,      ry + rh],  # left
+    [rx + rw, ry,      rx + rw, ry + rh],  # right
+  ]
+
+  !(edges.any? { |ex1, ey1, ex2, ey2| segments_intersect?(x1, y1, x2, y2, ex1, ey1, ex2, ey2) })
+end
+
+def segments_intersect?(ax1, ay1, ax2, ay2, bx1, by1, bx2, by2)
+  dx1 = ax2 - ax1
+  dy1 = ay2 - ay1
+  dx2 = bx2 - bx1
+  dy2 = by2 - by1
+
+  denom = dx1 * dy2 - dy1 * dx2
+  return false if denom == 0  # parallel
+
+  t = ((bx1 - ax1) * dy2 - (by1 - ay1) * dx2).to_f / denom
+  u = ((bx1 - ax1) * dy1 - (by1 - ay1) * dx1).to_f / denom
+
+  t.between?(0, 1) && u.between?(0, 1)
 end