Hands-on labs for the things that get tested for real: query plans, algorithms, design, backend failure modes, and Rust. Short lessons, real engines, and everything runs in your browser.
The labs
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On a phone, add Deep End to your home screen first and save from there; it then opens like an app. iPhone: Share, then Add to Home Screen. Android: the ⋮ menu, then Add to Home screen. On iPhone the home screen app keeps its own copy and its own progress, so turn on cloud sync there too.