changes made:

1 alot of time to look at the original codes by Prof Hwang
2 added features of learning
15 june 2010
3 debug the problem
E:\EJS_4.3.0_100613\EJS_4.3.0\workspace\output\users\sgeducation\lookang\weexva10_pkg\ ';' expected
   if ("d2correct ".equals(_variable)) __d2correct _canBeChanged__ = false; // Variables.basic:34
by removing the space at the back of the variables declaration, which causing compiling error
4 recompile to fit width = 600.
22 decemeber 2010
5 add picture of tree by megabanjo2017 creative commons attribution cartoon house by PeterBrough thanks to idea from
6 created activities to support the learning