Tools for writing things down and drawing them out — Obsidian, Markdown, Mermaid, and Excalidraw.
Obsidian
Personal knowledge management on top of local Markdown files, linked together.
Markdown
The syntax that works in READMEs, issues, and docs everywhere — and the parts people get wrong.
Mermaid
Diagrams you write as text in a code block — drawings that show up in your diffs.
Excalidraw
A hand-drawn-feel whiteboard, well suited to design discussion and architecture sketches.