Adding a new mode?

[Nightime]

I would like to know how to going about adding a new Game Mode to my SM setup; specifically, something like "Endless Dance Master Mode", or something to that effect, but easier to navigate. I'm also debating between the select screen being:

-3 songs + Random
-4 songs
-4 songs + Random

Either way, the navigation between stages will be simple. (3 or 4 song banners +/- Random) appear on the screen in the cardinal directions (top, bottom, and sides... the Random will go to the middle if 4 + Random is used). From there, you have 20 seconds to...

-Select a song via double-tap, or via single-tap and letting the timer run out.
-Let the timer run out without a tap, and have it choose "Random" by default. (Whether or not it appears?)

Then, depending on the layout...

(3 + Random or 4 Songs)
-A "highlight" will bound around semi-random (dependant on the digits in your score) ala "Press Your Luck"... you can stop that with the "Start" button to randomly choose a spot.
-Let the timer empty, and the cursor will "land" on one to choose for you.

(4 Songs + Random)
-Press Start to choose the Random box.


All mods/difficulty setup will occur *before* the mode begins, usually with a minimum/maximum-type setting (for example, a minimum of LGT and a maximum of HVY will not play Beginner or Challenge...), and the difficulties used are displayed during the song-select, but not the mods.


Can anyone point me in the right direction?