More Mercury 3 development details

Author: Heliodex

Docs/src/content/docs/design/mercury3.md

@@ -3,6 +3,18 @@ title: Mercury 3 & Mercury Core
 description: An overview on the relationship between Mercury 3 and Mercury Core.
 ---
 
-Mercury 3 is a revival platform using a hosted version of Mercury Core as its source code.
+Mercury 3 is a revival platform using a hosted version of Mercury Core as its source code. This page provides an overview of the relationship between Mercury 3 and Mercury Core.
+
+## Development of Mercury 2
+
+As explained in the [History](/history) page, the source code of Mercury 2 continued undergoing modification after it was shut down in June 2024, being released as Mercury Core in September 2024. As such, Mercury 2 is not considered to be based on Mercury Core.
+
+Mercury 2 changed a significant amount during its 2 years of development. Many core pieces of the codebase were modified or rewritten, services were changed, and libraries used (many of which were in beta or early development at the time) were updated or replaced. As such, while Mercury Core shows clear resemblance with Mercury 2[^1] in 2024, the resemblance with a version of Mercury 2 from 2022 or 2023 is less clear. 
+
+## Development of Mercury 3
+
+The development process of Mercury 3 has been very different to that of Mercury 2.
 
 todo
+
+[^1]: These changes can be viewed in full, with code change history throughout the entirety of Mercury 2, in Mercury Core's [commit history](https://github.com/tp-link-extender/MercuryCore/commits/).