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If anyone is still struggling with the Hard badge, I highly recommend this walkthrough:
https://www.youtube.com/watch?v=ToJR-w-qEtM
You have to follow it to the letter until the mid-40's (which will require lots of saving and restarting), and then you can either continue to follow the walkthrough (I don't recommend that), or wait until he goes to sell the first Ice Tower. Instead of selling it so you can upgrade the Boomerang, instead wait a bit into the round to upgrade the boomerang. The money you save allows you to get out an upgraded banana factory even quicker. By the mid-60's I was spitting out a new Research Facility every round and have more defense than I knew what to do with.
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In answer to haloreach486 - I believe that the second track used to be the Tap Track (the one shaped like a water faucet). (They have added, and it looks like also subtracted tracks, since the badges were made. I am not sure that they still have the first of the two tracks needed for the hard badge, unless it is the Stream Track; I can't remember.) I hope this information helps.
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The game heavily lags once the balloons come so fast that they end up stacking. This makes the game unplayable and rather annoying.
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I've gotten to round 40 several times and the game keeps freezing just the balloons. My airplane keeps flying/firing and my spike factories keep pumping out spikes, but the balloons with the shell freeze and won't move or take damage.