Even if the creator of the game gave you permission to upload their game and make money for yourself from it, you still don't have the right to do so under Kongregate's terms. Games may only be uploaded by their legal owner.
The difference is time. Easy gives you 5 minutes per level, normal 4, and hard 3. Doesn't make much difference at the lower levels, but it can be noticeable at the higher levels.
Score is determined this way: (coins+clock)*multiplier. Multiplier is 1 for easy, 2 for medium and 3 for hard. I was unsure as to the best multiplier to use.
By the way, there is a mute button already (press m) as I find most Flash game sounds annoying.
What could be used for other levels, apart from the difficulty levels?
Turning of ship greatly improved. Firing a missile does not remove previous one, although only one missile can be on the screen at a time. Possibly change to time limit between shots?
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