This is lovely, only two suggestions I can think of :-
Option to have SFX only ("rattle-ker-chunk, rattle-ker-chunk, rattle-ker-chunk")?
Some way of game-ifying things more? A final score based on stop-rating, time taken, signals correctly passed?
Regarding sound - difficult, there is no ambient sound. We cut engine hum at the last minute as it messed with the music in the web player and couldn't find a way to get them to play nice.
If you finish a journey (hold left) you will get a journey report with that info summarised. An aggregate score might be something I investigate in future, but there are several features I want to get in v1.1 first.