This handy thing is only a full adder. It can't subtract or anything else.

On the left side, there are the first 16 bit inputs, the second 16 bit inputs are on the back side. (Unfortunately not visible) The right pins are the 17 bit output. (16 bit with a carry out / overflow) The two loose wires are for the power.

Logic gates with n-channel mosfets are quiet simple. I purposely don't use CMOS (Complementary Metal Oxide Semiconductor) technology, because then it would not be that simple to solder/route. You would have to watch out for the correct n- or p-type. And it works very good with n-channel components. The resistors are about 50kΩ (You should look into the datasheet for each components!).

A full-adder made out of NAND logic-gates: ("Carry in" operates in the same, way like "A" and "B" do)

The schematics of my FA. It's simple and consumes very little current (only for switching from on to off or vice versa):

All 16 chips are mounted on this "main board":

It would be possible to use the carry-in for subtraction. But in my case, I don't need it and so it's grounded with a jumper. (as seen on the left and middle area)