After getting the sonar functioning with the display I started to become more paranoid over 'is this enough?' or 'how can I make this more than a little one-trick project?'
Thinking of my 7-year-old nephew, who this project is going to be gifted to, and how a sonar is great for stationary games but what about when he's on the move? I initially tested the ultrasonic sensor by building a simple rangefinder that worked very quickly and accurately, so why not make this until do both with the option to choose? So that's exactly what I did.
On boot-up you're now presented with an option to use the unit as a sonar or a rangefinder! One button lets you alternate the selection, and if the button is held it confirms the selection and runs that option. The coding for this was a pain in the butt, but I got there in the end!
I'm rather enjoying how primitive the display is, oddly enough. It's a nice creative constraint and, I think, adds a nice character to the visuals.