Improved accessibility

We noticed that many players were struggling to understand some of the mechanics of the game as well as getting confused by some of the icons and therefore we wanted to make a small update to help explain the game better.

1.  The icon for "Build a Path" shows that "Cross over" paths are allowed (and indeed required)
2. The reset path button has been disabled during play mode to prevent players clicking  on it in an attempt to "return to edit" 
3. Stop button now has white text to help it read better
4. Added the missing "fast forward" button which increases speed x2 when enabled during play mode
5. Fixed a bug causing the audio to either disappear and/or ignore the audio settings
6. Level 2's challenge has been modified to help see the answer more clearly