after discussion with teachers

several request were made.

1. velocity convention to be direction left is negative while always showing magnitude to be consistent with this particular schools teaching practice.

2. bug fixed for tmax for the graph to show the tmax consistently

3. some text changes as explain by teacher in accordance to text used in A level now.
perfectly elastic == elastic
partial inelastic == inelastic
perfectly inelastic == perfectly inelastic

4. spring model for collision will be release in a different model as i want to keep this version with event handler.
watch out for that :)