Write an RPG in 24 hours, during November, in the Pocketmod format, without any numbers. Hard enough for you? Run as part of NaGaDeMon http://nagademon.com
I'm writing mine straight into pocketmod-sized pages (so I can gauge how big they'll be) and am using a 10 point font. Which is slightly too small for really easy reading IMO (I prefer 11pt), but any bigger looks fucked up on such a small page.