Keyboard Listeners on Custom Interactions?

Dear Interest Group Members,

I have a general question about Keyboard Listeners and progressive enhancement (or graceful degradation depending on your perspective).

My question is, when one is building a custom interaction, e.g. re-arranging kicked soccer balls on a soccer field containing kicked balls, does one have to listen for additional modifier keys that are not required to perform the move? Or is it fine to just listen for the required keys (e.g., the Arrow Keys) that perform the move? 

For example, say you grab a ball from the group of kicked balls on the field by pressing Space, and then move that ball right by pressing the Right Arrow key, and then drop it by hitting Space again.

My question is specifically referring to when the ball is grabbed and being moved with the Arrow key. We are listening for the Arrow keys, and not any additional modifier keys (e.g., ALT, Control, Command) since they are not required to do the move. However, in our implementation, if you press a modifier key, e.g., ALT plus Right Arrow, the grabbed ball stops moving. It only moves when pressing an Arrow key by itself (or any other hot keys we are listening for, e.g., a number key will jump the ball to that number on the field). 

Should the ball keep moving when a non-required modifier key is pressed at the same time the Arrow key is pressed? I’m thinking no, and that our implementation is fine, but I wanted to hear what others thought about this.

Here’s a link to the simulation Center and Variability, if you want to try it out. Warning, this simulation has little to no description, so it is not screen reader accessible, only keyboard accessible. You need to kick some balls before you can re-arrange them to play with the median.

Thanks in advance for any thoughts on the pressing of un-required modifier keys in this group sort interaction.
Taliesin

https://phet.colorado.edu/sims/html/center-and-variability/latest/center-and-variability_all.html
‪Center and Variability‬
phet.colorado.edu


~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~
Taliesin L. Smith
talilief@gmail.com 
taliesin.smith@colorado.edu 

Inclusive Design Research Specialist
PhET Interactive Simulations
http://phet.colorado.edu/
Department of Physics
University of Colorado, Boulder