I have a Match Two game similar to the bejeweled board. I am rewarding the player on speed of score. If he scores X in Y time , he gets a bomb. The time window is not rolling but discreat.
I check what the users score was in last X seconds after every Y seconds and reward him. The issue is the reward is a bomb which explodes 9 tiles. (I've dumbed down the score of the tiles exploded by bombs) Now that score will be counted in the next user score check and if the user made of more pair he will be given another bomb and this continues.
So once the user gets a bomb it's very easy to get it again and keep getting it. Which ruins the uniquness of the bomb. If I say hey let's not count the score because of the bomb that way the user will have to start all over again to get a bomb and if we have Z types of bombs one better than the other it would be impossible for the user to get all the bombs. If the score keeps on restarting.
I'm having a hard time finding the middle ground in it. Any ideas?
Also for special items, what seems to be better roll over time windows or static time windows?