Cryptarithms vs Manual Override

The ability to sum numbers and perform logical reasoning are the only skills required for solving cryptarithms. Nevertheless, these puzzles are often witty and challenging to solve. A cryptarithm is a mathematical puzzle where digits in an arithmetic equality are replaced by letters. It is defined so that distinct letters correspond to distinct digits. Moreover, when the letters are converted back by the original digits, the resulting equality must be valid. The problem is to find the original digits. 90 сryptarithms with their translations to 6 languages are presented. Enjoy!

A hands-on introduction to the command line and SQL. You type the commands. No videos, no syntax tables to memorise. Each lesson hands you real material and a question you have to answer yourself, and you answer it by typing real commands. Get one wrong and you get a real error message, worded the way a real terminal words it. WHAT YOU LEARN · Filesystem: pwd, ls (with -a / -R), cd, cat, find · Text: head, tail (with -n +N / -n -N), wc, sort, uniq · Search: grep, with -i / -R / -F / -n and regular expressions · Compare and verify: diff (normal and -u unified format), sha256sum · SQL: SELECT, WHERE, ORDER BY, LIKE, JOIN, GROUP BY / COUNT / HAVING · One habit running through all of it: any conclusion should be something a stranger can re-run command by command HOW THE COURSE IS BUILT Eleven lessons, each with one answer you have to find for yourself. The material is a virtual filesystem and a real SQLite database. Commands run in a sandbox and never touch your device; the database is read-only, so no query you write can break anything. Most puzzles accept more than one solution: the way you already know works too. ALSO INCLUDED · Offline syntax manual and table-schema reference, always one tap away · Practice mode (with the full course): the terminal and database with no lesson flow, just type · Command and flag completion, Tab completion, history recall — built for touch · Three colour schemes, text size, reduced motion, haptics toggle · Runs entirely offline. No network, no data collected, no account, no ads ABOUT THE STORY A fictional storyline ties the eleven lessons together: you are reviewing an obsolete course package scheduled for deletion, and you use each command you have just learned to check the material against itself. The story is the premise for the exercises, not a substitute for them — every conclusion is still one you type out yourself. The prologue and the first three lessons — the whole command-line half — are free. Lessons 4 to the finale (the SQL half) and practice mode are one purchase: no subscription, no ads, no account.