[kaoD]

I think it's just a case of leaky abstraction. I'd change the API to something like:

    robot.action = { action: 'jump' };
    
    robot.action = { action: 'move', amount: 4 };

    etc.

Or if you want to keep the action creators:

    robot.action = robot.jump();
    
    robot.action = robot.move(4);

Which makes it obvious that there can only be a single action per loop call.

[reacweb]

Or the action could be the return value. IMHO, trying to guess the physical model by experimentation is painful. Why not propose a debug button to display the state of variables during the execution of script.

[positivecomment]

Exactly, the function should not be responsible to see if robot.action has any existing value. It should just return an action depending on the state.

[always_good]

Another idea is to return a map of actions.

    { jump: true, move: 4, shoot: true }

Making the user increment a nonce and use the remainder operator just to do multiple actions simultaneously is pretty heavy.