A servo would be a better idea, they know where they are position wise, but has less than 360 degree movement
With this you could just tell it to move to position A to be flat and position B to empty
A stepper has 360 degree movement but no idea where it is position wise, you need things like end stops so it knows where its at or how far to move
On power on you need to work out where you are, so you move until it hits a endstop, from there you can move n steps to get to the next positions then n step back in the other direction to move back.
you also need to get familiar with programming the arduino [www.arduino.cc]
Here is an eg that is almost what you want with a servo motor [www.arduino.cc]
Just need to add in some time code
With this you could just tell it to move to position A to be flat and position B to empty
A stepper has 360 degree movement but no idea where it is position wise, you need things like end stops so it knows where its at or how far to move
On power on you need to work out where you are, so you move until it hits a endstop, from there you can move n steps to get to the next positions then n step back in the other direction to move back.
you also need to get familiar with programming the arduino [www.arduino.cc]
Here is an eg that is almost what you want with a servo motor [www.arduino.cc]
Just need to add in some time code