 The task of designing the ZX81 's case again fell to Rick Dickinson , who produced an updated version of the ZX80 's wedge @-@ shaped case . This time round , the design team were able to use injection moulding , which enabled them to deliver a higher @-@ quality case . Dickinson originally envisaged the ZX81 as " an expandable range of boxes following a vaguely modular approach with a common width " , though this approach was eventually dropped . From start to finish , the design process took about six months . 
