beatmania IIDX 7th Style is the 7th game in the beatmania IIDX series of music video games.
Core gameplay remained the same on 7th Style. 5-key mode has been changed from a difficulty to its own modifier, allowing it to be used on any difficulty level as with normal charts. A new spinoff of Expert Mode also debuted, Daninintei (Class) mode, a mode containing a series of courses ranked so that each course is harder than the last, the highest rank course a player can beat in Dan mode is often used to compare players. Dan mode would have significant integration in future styles implementing the e-Amusement system, which could save a player's rank, and may also restrict access to specific songs based on their current rank.
The home version of 7th Style was released several years later in 2004 for the PlayStation 2. It contained two preview songs from 8th and 9th Style, as well as some revivals. 5-Key was left as a mode instead of a modifier (unlike the arcade version), and unlike future home releases, the special Extra Stage methods were not present. Masters Mode was also introduced as a modified version of Survival Mode.
Source: Wikipedia, "Beatmania IIDX 7th Style", available under the CC-BY-SA License.