Modify shift controls to be less sensitive

Instead of using MicroBit.accelerometer.getX(), perhaps I should use MicroBit.accelerometer.getRoll() instead and compute where the player wants the block to be from that. The current controls are far too sensitive and quite hard to use, an angle-based control system would be much easier to use. 0° could be 'middle', I then just need a half and full left/right value for both sides (somewhere between 0° and ±180°).