The Password Game, Rule by Rule: What Each One Wants and What Breaks It

Rules 1 to 4: the normal form

Five characters, a number, an uppercase letter, a special character. Pick an uppercase letter that is not a Roman numeral — A, B, E, F, G, H are safe — because rule nine is coming.

Rule 5: digits add to 25

Every digit in the password counts, including the ones later rules force on you: the captcha answer, the leap year, the length, the time, the hex code. Zeros are free. Keep this rule in mind every time you add a number.

Rules 6 to 9: months, sponsors and Roman numerals

A month, a sponsor, a Roman numeral, and then the numerals must multiply to 35. XXXV alone is 35. The trap is that only uppercase I V X L C D M count, so write 'contra', 'may' and 'december' in lowercase or their capitals join the product.

Rules 10 to 15: the world outside

A captcha sum, today's day of the week, a two-letter element symbol with the right capitalisation, tonight's moon phase as an emoji, a country, a leap year. 'He', 'cuba' and '2000' are cheap answers. The moon and the day change, so a password that worked yesterday may not work today.

Rules 16 to 18: Paul, the length and the colour

Include the egg. Include the length of the password as a number — which changes every time you type. Include the six-character hex code of the colour shown, in lowercase, remembering its digits count toward 25.

Rules 19 and 20: the clock

Paul hatches: swap the egg for the chicken and add caterpillars, at least three, and he eats one every thirty seconds. Then the current time in HH:MM, which changes every minute and whose digits also count. Get everything else green first, then add the time and re-type immediately.