Or just make the cart a bullet and set angle of motion to (Zipline.Angle+45) ...
Well the zipline isn't just a line, here, I drew an example. I would have this over the actual object(s) he ziplines on. I suppose I would be able to do it with a bunch of individual objects, but is their no more efficient way?
Edit: I tried what I just said and it look horrible, the player just glitches around to each segment.
You don't need to check for collisions every tick. At first, sure, check for the inital collision with an invisible sprite at the start of the zipline. Then if collided with that sprite, set a variable "isOnZipline" to true. Disable platform behaviour. While that variable is true, then move at angle. Until it collides with another invisible sprite at the end of zipline, then set the variable to false and enable platform behaviour. Should dismount automatically using the gravity from the platform behaviour.
Right, but what you said with the angle seemed a bit off.
<img src="https://dl.dropbox.com/u/44188718/Help/zippy.png" border="0" />
Thanks for all the feedback!