Circuit 2 - Odd Parity Checker w/ 7 segment display (2s bit Complement)

The next circuit that I made is an Odd Parity Checker with a 7-segment display. To begin the creation of this circuit, it is best to examine it by breaking it into two components. The first component of the circuit would be the Odd Parity Checker. I began by making a truth table (attached below) and utilizing a K-map to simplify it. To my surprise, it turned out to be a large expression which was something I was not looking forward to. I then saw a pattern within the truth table and realized that it had a pattern that was similar to an XNOR truth table. I then did extensive research about odd parity and I found out that the very large expression was possible to be simplified with the utilization of XNOR gates which I previously shed light on. Even though we did not have an XNOR logic gate, using an XOR and a NOT gate would be a simple remedy to this problem. After connecting the simplified XNOR gate to the light, we would then be able to identify if there was an Odd Parity, basically showing if there was an even amount of 1s that were selected. The LEDs on the right would demonstrate exactly which light was on and that was caused by a direct connection from the input to the LED. This would conclude the first part of the circuit. For the second component, we would look at how to have the 7-segment display show a numeric value if the Parity Light was not on. I realized that manually connecting the wires to each segment for each number would take YEARS so my next solution would be to use a 7-segment decoder logic gate. What this does is that it takes 4 inputs and connects those to the 7-segment display with each perspective letter. For some reason, this part was the longest and hardest of this entire process because even though it seemed correct, the display would not show any numbers. After doing many practice circuits, many failed attempts, and even guidance from my peers,  I was finally able to achieve success by simply having the 7-segment display show numbers.  Something so simple took literal hours to complete.  The next challenge of this portion was to figure out a way to only activate the 7-segment display once the parity light was off. After lots of research and countless trials, I found success by adding a wire to the row with the output of the parity display light. I then would connect that additional wire as an input for the NOT gate to flip the outcome value which basically is always the opposite of the parity light. I would then connect the output of that wire to the "blanking" input of the 7-segment decoder which would turn off the 7-segment display to turn off if the parity light was on which ended up being the solution to how to only have one on or the other.   

Revision: After talking to Dr. Pasquale about ways to improve upon my project, I was told to make it so that I would include a parity bit which made my circuit still have the 4 inputs but in reality 3 inputs. Thinking of a way to create such a bit that would turn the parity check light off, turn the 7 Segment Display on, and display the correct inputs troubled me very much. But after lots of trial and error, I decided that a simple remedy to this would be to create a truth table for the parity bit. Every time it was an even amount of bits on, there would be a 1 as the output. After writing that out and doing the KMap for it, I realized it was the exact same as the circuit I had already made but with another input. So I implemented that into my circuit and at last, it worked! When there was an even amount of bits selected, the parity light would go off, once you select the parity bit to turn on, it turns off the parity light and instead display the value of those previously selected bits on the 7-segment display.