Streamlining of Levels

This update exists thanks to jinke, Ömer Talha and MW-Systems who play-tested frame. Due to their invaluable feedback I could identify several bottlenecks in the level design. Based on that I implemented a lot of features to improve "communication" with the player and provide a more streamlined experience:

• the level exit can be clearly visualized, to give players some direction
• an animation demonstrating the connections between frames
• an animation demonstrating the connection between buttons and actions
• redesign of several levels, where it turned out that the level-design based communication was a bit too subtle
• redesign of arrows (show movement of objects), to increase visibility
• unlocked hints are shown in the menu, are enumerated and stay unlocked when restarting level
• change of paint-gun behavior: the paint-gun had a subtle but important behavior that was difficult to understand for players. So I changed the paint-gun to behave as players expect.
• several new "tutorial-levels". With these some hard too grasp mechanics are introduced slower and thus difficulty spikes are flattened.
• redesign of some levels to avoid exploits/cheese
• timed buttons give an audio feedback

Additionally to all these improvements there is also a new level, playing with the paint-guns capability to shoot through frames.

Last, but maybe least, there are two bug-fixes, too. One bug could lead to invisible walls in very specific scenarios and the other one could lead to the same sound being played twice at the same time.