How to design a simpler Version of CARDIAC (Cardboard Illustrative Aid to Computers)? I'm trying to make a simpler version of CARDIAC for only performing addition. Now, I am encountering several problems in making something similar and looking for some ideas (I'm new to Computer Architecture).

Here's an excerpt of what CARDIAC is (Wikipedia):


  CARDIAC (CARDboard Illustrative Aid to Computation) was a learning aid
  developed by David Hagelbarger and Saul Fingerman for Bell Telephone
  Laboratories in 1968 to teach high school students how computers work.
  The kit consisted of an instruction manual and a die-cut cardboard
  "computer".
           The computer "operated" by means of pencil and sliding cards. Any arithmetic was done in the head of the person operating the
  computer. The computer operated in base 10 and had 100 memory cells
  which could hold signed numbers from 0 to ±999. It had an instruction
  set of 10 instructions which allowed CARDIAC to add, subtract, test,
  shift, input, output and jump.


Basically it's a simple illustration of how a computer works internally to do basic stuff(as explained in the excerpt). I'm only trying to do addition but I am trying to find a way to show what the output is.
Here's how I thought it would be:
I would use a 16-bit register with binary base and 10 memory cells. I  guess this should be more than enough for a basic addition illustration.

Now my problem is, I'm not very sure how to output the values. Let's say for example, I input 10(binary for 2) in register R1 and 1(binary for 1) in register R2. Now this goes to the ALU, which calculates the addition immediately and places it in register R3. This would be represented using arrows and sliding cards(values for R1, R3 and R3) in specific slots on the illustration.

My problem is, now that I have the value in R3, how do I output it using that cardboard illustration? Also, does the ALU work as logic gates to calculate the sum?
You want to make a binary adder. You can make one out of boolean logic gates. Your register will be based on your binary adder. It is not a more simple computer than the CARDIAC computer, because the CARDIAC works with base ten and the beginner does the arithmetic by hand. Boolean logic is taught much later in school than addition in base ten.