Discrete transistor computer progress report 1

I've been working on this project for a little while now, and I've finally managed to finish a 4-bit adder! It's just a small part of the total project, and I've still got a long way to go, but it's some visible progress.

One thing I found out when putting this together was that my original design was far too compact and made it difficult to keep components apart when soldering. I've spaced everything out a bit more, but some of the solder joints are still a bit closer than I'd like, so some of the connections are a bit finicky.

Here's some pictures of the adder (although I forgot to connect the carry-out before taking them):

Here's one with the LEDs I used to test that it was working correctly:

And here's the diagram for the design I ended up using to make the 4-bit adder: