Tools

String transforms — each tool is its own inverse or a paired encode/decode:

• transform — visual threading-macro pipeline: chain transforms, see every intermediate value, reversibility indicator
• rot13 — Caesar cipher by 13; its own inverse
• base64 — Base64 encode/decode
• url-encode — Percent-encoding for URLs

Generators:

• QR code — generate QR codes as SVG, inline, no server

Algorithms:

• dijkstra explorer — algebraic path problem: one solver, three semirings (shortest, rainwater, widest)
• trapped rainwater — elevation map to retained water volume; O(n) two-pointer, SVG visualization

Editors:

• pasted file editor — paste/drag-drop file editor (adapted from Simon Willison)