How do the two modes work?
Binary Mode (0-15): Visualizes a 4-bit 2's complement system. The red needle strictly mirrors the blue needle (V-shape) to point to the mathematical 2's complement of the active number.
Decimal Mode (0-9): Visualizes single-digit 10's complement. The red needle sweeps in the opposite direction to perfectly point out the 10's complement value (10 - X) of the active number.
Why does the red needle overlap at 8 and 0?
In a 4-bit 2's complement system, the numbers `0000` (0) and `1000` (-8) are their own negatives. When you point the blue needle at these numbers, the red (opposite) needle must point to the exact same value, causing them to overlap perfectly.
