MTG Forge has at least 21,000 lines of code. (I say "at least" because that number doesn't include CardFactory which has a lot of redundant code. CardFactory another 16,000 lines itself which makes for a grand total of 37,875 lines.)
It is hard to picture 21,000 lines of code but if you wrote 100 lines of code a day it would take you at 210 days, so you can easily see why MTG Forge took about a year to get it up and running. This doesn't include specific bug fixes which tend to take up tons of time and only account for a tiny bit of code.
MTG Forge’s source code is roughly the size of Oliver Twist by Charles Dickens. When the source code is compressed the size is 350 kb which is the same Oliver Twist. Oliver Twist is about 400 pages long, although the exact number of pages will vary from book to book, and has around 161,000 words. And for what it is worth, the source code is 1.78 MB uncompressed and Oliver Twist is 914 KB, so MTG Forge’s source code is about twice the Oliver Twist.
Computer programming is like writing a novel or building with toothpicks. It can be done, but it takes a lot of time. MTG Forge is by far the longest program I have ever written.