fix some shapes generation and draw a grid of shapes for an overview

engine/shape.hpp

@@ -21,7 +21,7 @@ public:
     template<int div>
     bool create(float w, float h)
     {
-        static GLushort idx[div * div * 6 + 4];
+        static GLushort idx[div * div * 6 + 8];
         static vertex_t vertices[(div+1)*(div+1)];
         create_impl(w, h, div, idx, vertices);
         return create_buffers(idx, vertices, sizeof(idx), sizeof(vertices));