before Qubits

Here a 4- bit computer like 64-bit modern computers.

The game intractable with wires of computer transistors. There some logic gates(AND, OR , XOR, Half Adder, Full Adder) that will be used for logics.
Luckily, Now you can add 2 digital numbers and observe how the computer computes with its transistors. It's a 4 bit adder computer.

Have a fun!!!