Yesterday, the best answer is: 2x^2.  (Contributed by dnialh. Good Job!)
dnialh solved the puzzle at 20:41:22.110; length: 8
dnialh solved the puzzle at 20:41:33.696; length: 8
dnialh solved the puzzle at 20:41:36.101; length: 7
dnialh solved the puzzle at 20:41:37.134; length: 7
fire solved the puzzle at 21:13:50.959; length: 8
asdf solved the puzzle at 22:55:25.186; length: 8
asdf solved the puzzle at 22:56:05.494; length: 8
asdf solved the puzzle at 22:56:15.814; length: 7
m1o9n6s8t8e3r solved the puzzle at 00:27:42.687; length: 8
m1o9n6s8t8e3r solved the puzzle at 00:27:50.762; length: 8
m1o9n6s8t8e3r solved the puzzle at 00:27:53.314; length: 8