Redstone - Random Number Game

This redstone device is a random number game, where you must input a number of your choosing. The computer will then generate a random number and add it to yours. In the next room the sum of the two numbers will be displayed on a 7-segment display. Your task is to input the number that you think the computer has generated into a specified input panel, where your input will be tested on an AND gate array. If you have entered the same number as the computer has generated, some lamps will light up signifying that you have guessed correctly.
I know it's not too hard to work out the correct number, but the goal of this build was not to make a difficult challenge. The goal of the build was to see if it was possible, and if so; to see how much redstone it would take me.

Please let me know about anything that doesn't work so that I can get around to fixing it!

Note: Make sure all of your inputs are done in binary.

Hope you guys enjoy :)

At the moment there is no simple way to reset the machine, but if you know anything about redstone memory, you can reset it by manually resetting the D-Flipflops (there are two of them).
If you don't know what I'm on about, then simply reinstalling the map will reset it as well.

Specs: 2 x 7-segment display units
5-bit binary to Binary Coded Decimal Converter (BCD)
2 x 4-bit decoders
- outputs are hooked up to an AND gate array.
Random 4-bit number generator