BuildBrief turns a two-sentence app idea into a build-ready plan in about 15 minutes. Four prompts, run in any AI chat tool you already use: an honest idea validator, a screen blueprint, a ready-to-paste build prompt for Lovable/Bolt/Cursor, and a 48-hour launch checklist. Each prompt auto-fills from the last one, nothing gets retyped. One self-contained HTML file. No account, no software to install.