DNA Spin was a side scroller. You had a 3D model of a skier placed on top of a 2D background of a ski hill. There was just an invisible wall thing in front of the picture to act as the ground/collision.
You skied down a ramp holding down the spacebar and various arrow keys. Left and right made you spin, up and down made you flip. Little bars showed how much spin and flip 'energy' you had. You'd realease the bar at the lip of the jump and the skier would do the flippy spinny thing. z, x, c, v were grabs. Hopefully you would land upright, and have enough speed for the quarter pipe at the bottom. Same flippy-spinny rules apply there.
What DNA Spin did right:
-Graphics - bright, 3D, cartoony, lots'a blue.
-Side view (tricks look cooler, easier to time flips so you land upright, easier to make for the developer then a full 3D game)
-Landing off balance slowed you down
What DNA did wrong/you need to do:
-Make the physics realistic. You could flip and spin on flat ground in DNA, not good.
-Holding grabs = more points. DNA spin gave you the same points whether you did the grab for a split second or 2 seconds. Bad!
-Count flips and spins seperately - One couldn't do Misties or Rodeos in DNA - a flip with a spin was just scored as a flip. If the player spins 3x and does a front flip, its a Misty 1080!
-Bigger - usually the jump in DNA spin landed you right at the bottom of the quarter pipe, and you wouldn't have enough speed to get up the wall. Even if you just do a 2 element park (1 jump, 1 qp), make sure both elements can be used well.
-Make sure there is room for the player to turn around 180 for switch tricks before each jump/rail/qp. Obviously switch tricks = more points, but don't want everyone ALWAYS doing switch tricks, so maybe popping a jump switch gives you less air.
-High scores list!!!
-No music - someone will always hate it, no matter what you choose.
-If you can't get good sound effects, don't use any. Otherwise it just becomes annoying and I'll turn off my speakers.
-Don't bother with different skis and sponsers and companies and gear - just takes more time.
-Gameplay is ALWAYS more important then graphics. Just make sure graphics get the message across that I did 720 with a Mute grab in the last 360 degrees of the spin.
-If a flip with lots of spin energy is a rodeo/misty, then a spin with a little flip energy should be an off axis spin - make sure thats worth extra points over a normal spin!. A jump with equal amounts of flip and spin energy should something special... lincoln loop maybe.
-Doing a trick once = 100% points. Second time the same trick is done = 75% points, third time = 50% points and so on. Don't let doing the highest scoring trick over and over again be the only way to win.
That should cover it.