Lemmings is a puzzle-strategy video game developed by DMA Design (later Rockstar North) and published by Psygnosis. The concept was conceived by Mike Dailly, who during a lunch break animated a demo of tiny characters walking in a line — prompting Russell Kay to remark that a game could be built around it. Released for the Amiga on 14 February 1991, players must guide a tribe of hapless lemmings through 120 hazardous levels split into four difficulty categories — Fun, Tricky, Taxing, and Mayhem — by assigning each individual a skill: digging, building, blocking, climbing, bashing, bridging, or exploding. A quota of lemmings must be saved to complete each level. The game was a massive commercial success, selling 55,000 copies on its first day and accumulating over 20 million sales across 21 platforms. It cemented DMA Design as a world-leading studio, made David Jones a millionaire at 25, and launched a long-running franchise of sequels and spin-offs.