This HyperCard stack computed the wheel ratio for each of my bikes from tooth counts of the front wheel rings and cogs in the rear cluster.
The Gears stack simulating my first racing bike, Trek 1500.
The screen showed a 3d view over the bicycle-appropriate handlebars.
A billboard in the distance visualized the the ratios on a logarithmic scale. This showed duplicated ratios and suggested shifting strategies that would avoid them.
You could pedal the bike by clicking left then right peddle buttons as they appeared. Manual dexterity limited you to believable cadences.
You could shift front and back gears with appropriately placed shifters and see how that effected the speed showing on the bike's handlebar mounted speedometer.
The rest of the scene was a view of the long road ahead with mountains in the distance.
I started bicycle riding in ernest around 1985. Soon after I wrote this stack to compare gear ratios of my new racer with my older bikes.
Later I added more bikes to my collection and added friends bikes to my stack. I added a second background that looked like a mountain bike when that became popular.
The pedals are buttons. If you click them in an alternating fashion then the speedometer will read out miles per hour for the gears you have selected.
The numbers on the right hand side of the screen are the gear inches of each gear combination. This is the same as the diameter of a non-geared wheel (remember those old time bikes?) that would go the same speed.