BBC Basic (previously) was a well-regarded implementation of BASIC made for use in schools in the UK. Now you can play with it online [via] in a web-based environment that's far nicer to use than a real BBC Micro. The in thing is to make spectacular demos that fit in a tweet.
BBC Micro bot runs your tweet on an 8-bit computer emulator. Below is output from 1000 programs that different users submitted to the bot. Click any to see source. The tweet sized programs are written in BBC BASIC (1981) a very fast implementation of the language by Sophie Wilson who later created the ARM architecture.