I was reading up on Gödel, Escher, Bach and then Scott Kim (he was a student of Douglas Hofstadter) popped into my mind. His early Inversions book blew me away back in the 90s, and when he ambigrammed my name I recall being so overjoyed. You might recall he designed the (once) famous Sun Microsystems logo which you can rotate and still read in any direction:
Check out more of his work from these links (and flip your screen upside down):
Jimmy Stewart, 1997
J.S. Bach, 1981
You made my day John Made: so much to be done and nothing that an open mind can’t solve!