Update ideas

IDEAS.txt

@@ -13,6 +13,7 @@ These are some ideas about what you can do with this game:
 - Add OpenGL (or other accelerated) rendering, with true 3D, true color,
   antialiasing, texture filtering etc.
 - Add movement inertia.
+- Add possibility to load levels at runtime from a file.
 - Improve SW rendering on PC, e.g. use full z-buffer, particle effects etc.
 - Try to add screen space filters, like screen space antialiasing or pixel art
   upscaling algorithms.