I remixed just now to include

1. t = t + dt; // because students want to verify that a curved track, time is shorter and straight track time is longer.
2. change color scheme to suit blue=displacement , magneta=velocity, red=acceleration no particular reason, just consistent with my other applets i guess.
3. added sliders and numbers to be display like TE PE KE v instead of just bars
4. added the graphical panels on the right to aid visualization of velocity & energy vs time
5. change back to the evolution differentiation page with Runge Kutta 4th solver method ( to reduce carry forward errors under euler solver method ) instead of the incremental evolution page
6. added drag force to the equation  d(coaster_sv)/dt = sdd(coaster_s,coaster_sv) -b/m*coaster_sv // http://www.myphysicslab.com/RollerSimple.html
15 june 2010
7 remove the PE KE and TE from main panel and made bars display on the left which made the display nicer i thought
8 width = 600 http://sgeducation.blogspot.com/2010/06/ejs-open-source-roller-coaster-physics.html
15 june 2011
added circular loop to the drop down menu
remove stuff to debug a web deploy problem that is fixed i think after removing the closest =true in some sliders.
revert to older ODE that has codes to account for KE+PE = TE conserved

Feedback are welcome!
credits to Michael Gallis and Wolfgang Christian.
I only remixed it, i did not make this! :)