I wrote a C program to draw out the motion of a particle with fixed mass and charge inside a "magnetic bottle," which is basically a magnetic field that tends to trap particles.

Click here to download the zip file that contains the executable and another necessary file (keep it in the same directory).

Here is an example of how a particle is trapped inside a magnetic bottle.

The program was developed from the early screenshot seen above to the much nicer looking one below:

It also plots projections of the velocity, B-field and force...  It can rotate the view-points...

And also works with 3D glasses!!