redesign the simulation a little bit
set td = 0;
add check boxes for vision of flying in air and exploded to be compared with sound check-boxes
activate time
add background color to buttons and slider
add hints
vi is initial velocity of firework projectile
vf is exploding projectile velocity
add input field for game like checking of answers so now the answer is assessed against computed answer of delta s= 330*delta t assuming speed of sound in air is 330 m/s

11 august 2011
added majulah Singapore image with select-able check-box to celebrate image taken from there used under fair use.