Ex-Tencent engineer, full-stack architect, indie hacker. I build small tools and SaaS for global users with AI-assisted coding, and document the code, the products and the growth experiments behind them.
sheetdo.com — Master spreadsheets by doing.
A free, in-browser practice hall for Excel and Google Sheets formulas. You type a real formula into a real sheet and get pass/fail in milliseconds — nothing to install, no account, and no server evaluating your answer.
- Practice hall — 35 graded challenges, from everyday arithmetic to XLOOKUP questions that show up in job interviews
- Formula guides — VLOOKUP, XLOOKUP, IF, IFERROR, SUMIF, COUNTIF, LEN, MID and more
- Micro-tools — CAGR calculator, freeze panes, merge cells, duplicate highlighter, dropdowns
- Cheatsheets — formulas and keyboard shortcuts you can print
Built with Astro (fully static) and Univer Sheets (the formula engine runs client-side). Available in English, 简体中文, 繁體中文 and 日本語.
- Blog: sheetdo.com/blog/
- X: @marsbuildlog
- Threads: @marsbuildlog