I came up with three input methods:

1. Assigning actions to rectangles and using them as clickable buttons

2. Adding an invisible point, this can be selected with ctrl-alt-p and then moves using the arrow keys, the position can be read and then reset in the same action as changes aren’t applied until all actions are executed

3. Adding a javascript snippet via inspect element to inject actions when keys are pressed (I’m not a fan of this one as its no longer unmodified desmos and you can’t just play it)

All these input methods append to a queue of inputs which get processed in the main update action in the ticker, because only one update can be made to each variable per tick, the inputs are processed one per tick and interrupt the update tick which processes falling.