I didn't see anyone post the obvious strategy as far as escaping a pin -> get your alliance partners to help! Teamwork pretty much always wins
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As for the original post, fans on defense, not only is it hard to make them powerful enough to be effective, but it is hard to angle them correctly. Any fan pointed at any angle other than parallel with the ground would change the normal force on the bot, which could cause it to be ruled a traction device in violation of R06 (I'm not 100% sure on whether it would qualify, but I believe I recall a GDC post about altering air pressure to increase traction, again, not 100%).