[b]Reset[/b] will [u]reset[/u]  everything from the beginning (Nothing to be remembered!).
You should use [b]_initialize()[/b] instead of [b]_reset()[/b] 
to restart the simulation with different user setting.
(You need to and add code to initialize page to initial values)

For examples:
There is a slider to set vi, add [b]_initialize()[/b] for [u]drag[/u] action
Add the following code to initialize page
[code]
t=0;
x=xmin+size;
vx=vi; // vx will be set to user selected value
[/code]
You can also have a slider to set vx.
Then, the code in the initialize page might be something like:
[code]
t=0;
x=xmin+size;
[/code]