Oh No! More Lemmings (ONML for short) is a computer game expansion to the Psygnosis game Lemmings. Sometimes referred to as the "data disk", it contains 100 unique single-player levels and six new music tracks. The Amiga version also includes 10 two-player levels. This game is not the official sequel to Lemmings, a title that goes to Lemmings 2: The Tribes.
The game requires either the install disk from the previous Lemmings, or, in a standalone version, the game manual, for use as a copy protector. The new levels are separated into five difficulty categories (Tame, Crazy, Wild, Wicked, and Havoc), each with 20 levels.
Unlike the original game, none of the levels borrowed graphics from other Psygnosis titles. In one level, "Inroducing SUPERLEMMING", the game clock is greatly sped up. Also unlike the original Lemmings, each level is unique; no levels appear in multiple difficulty categories with different amounts of each skill.
The gameplay is effectively identical to the original Lemmings game. However, while the first few levels for the Fun rating in the original game are tutorial-like, the Tame levels in ONM Lemmings are just simple levels without hints on how to complete them.
All subsequent levels are considerably more difficult than those from the original game and become tougher at a much greater rate. Some players consider the Oh No! levels to be more entertaining, as they present a much greater challenge than those of the first game. The quota for the skills on many levels is set so that you need to use them all up, thus giving only one possible way to complete many levels in ONML.