You should not need a new computer :P And while it may seem that you do a level perfectly, you have most likely hit a key an extra time (which makes you lose ten point, and thus the perfect medal). I thought the same thing at first, but I was wrong. Great game.
Interesting concept, but can be very frustrating. Bonuses seem to be doled out at random sometimes, but maybe I just don't understand how they are calculated. Tip for newbies having trouble: run through the tutorial until it gives you the four bonus tiles, then skip the tutorial. You'll start the game with those four extra bonus tiles.
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