Mitt Romney must be using a special calculator for his tax plan, which proposes to cut top rates by 20 percent without raising taxes on the middle class or increasing the deficit. This fun website romneytaxplan.com, funded by the Democratic National Convention, attempts to help explain the magical math behind Romney’s tax plan. It’s an easy, single-serving site that asks you to just try to click a button to see the explanation. But clicking the button is harder than it looks. You’ll see. The site has already been tweeted over 26,000 times and liked on Facebook over 215,000 times. Check it out for yourself.