more discussion with teacher

My team have tested the EJS when designing our worksheet.

We find the following issues with the EJS.......
Error in field lines (refer to attached image):
1. The field lines are not drawn correctly. Everytime I vary the number of field lines, a different error in the field lines will appear.
Also, chances of error is particularly high if i use the slider bar to change the number of field lines. Error will likely occur when the EJS recalculate the field lines.
[color=blue][b]we solved the issue by allowing the Q2 to draw the field lines at different starting positions[/b][/color]

1. colour scheme: can we request for light background contrasted with dark arrows and field lines.

[b][color=blue]background is actual an equal potential scalar plot, the sim now remembers what the student select, u can also disable it for a white background.
field lines are now black and thick.[/color][/b]

2. Hide options to change colour of arrows, field lines and background. We felt it is not necessary for students to be able to change colour of arrows, field lines and background.

Thank you.