Mob that have 60-place inventory, that doubles as 60-line length program. When powered, loops through inventory, looking for special items (elements) that makes it do things like go one step forward, turn for set amount of degrees, pick up nearby things, dig, take and put things in chests, or place blocks. Each action consumes energy. Also there are special elements that marks start of subroutine, commands to run specific subroutine or repeat next command set amounts of time.
i can write it in more details, if interested.