68 challenges across eight tiers. Tier 8 is a warm-up; tier 1 will take an evening. Nothing is locked — play them in any order.
Match a valid IPv4 address — four numbers 0 to 255, separated by dots, and nothing else.
Match passwords of at least 8 characters that contain at least one digit and at least one capital letter.
Match a well-formed hand: exactly five cards, single space separated, each a rank from A23456789TJQK followed by a suit from SHDC — and no card appearing twice. Hands are always sorted by rank, ascending.
Validate the short two-field FEN: eight ranks separated by slashes, then a space and the active colour.
Match a valid CSS hex colour — a # followed by exactly three or six hex digits, and nothing else.
Match strings made up entirely of digits, with at least one digit.