The Extra Stage is a bonus stage that can be awarded by scoring well during the main set of songs.
How to Earn
It needs to be made clear that playing in Event Mode will prevent the ability to access the Extra Stage.
By default, all you need to get an extra stage is to score the equivalent of a
AA on your final song, assuming you played on either of the two hardest difficulties. Assuming ITG notation, that means Hard and Expert difficulties or DDR X notation, that means Expert and Challenge in 10 or upper.
There is no built-in restriction on whether the song must be a normal length song, a long version, or a marathon. There is no restriction on what mods are used to play that final (pre-extra) song.
How to Play/Setup
By default, StepMania automatally selects the extra stage songs depending on the song group of the last normal song you picked, and the default mods are "norecover" and "suddendeath".
Or, you can manually specify an extra stages for a song group by creating .CRS file in the song's group folder and change the bar by the battery. Place the files "extra1.crs" and "extra2.crs" in the song group folder. For example:
-- Songs |-- My Group |-- My Song 1 |-- (song files) |-- My Song 2 |-- (song files) |-- extra1.crs (Specified song) |-- extra2.crs (Specified song) |-- extra1.crs (Random song) |-- extra2.crs (Random song)
When it comes time to play an extra stage, StepMania will select the first (or random) song in the .crs file. In 3.9, add the next mods before save the extraX.crs: "battery,4 lives" instead of "norecover" (extra1.crs) and "battery,1 life" instead of "suddendeath" (extra2.crs). Don't forget to specify modifiers for the song too (see the CRS File Format).
Don't forget: extra stage CRS files belong in the song folders (e.g. "Songs/Vib Ribbon/"), not in "Courses".
A random song in Extra1.crs:
#SONG:*:(<difficulty>|<meter range>):(norecover|battery,4 lives),<modifiers>; example (Battery): #SONG:*:1..20:battery,4 lives; example (Pressure): #SONG:*:HEAVY:norecover,1.5x,reverse;
A random song in Extra2.crs:
#SONG:*:(<difficulty>|<meter range>):(suddendeath|battery,1 life),<modifiers>; example (Battery): #SONG:*:1..20:battery,1 life; example (Sudden Death): #SONG:*:CHALLENGE:suddendeath,3x,reverse;