#!/usr/bin/perl

use strict;
use constant PI => 4 * atan2 1, 1;
use SVG;

my $g = 9.8;
my $vx = 10.0;
my $vy = 0.0;
my $dt = 0.1;
my $r = 5;

my @cors = (0.95,0.9,0.8,0.7);
my @clrs = ('red','blue','green','yellow');
my $svg = SVG->new(width=>800,height=>600);
$svg->rect(x=>0,y=>0,width=>800,height=>600,fill=>'none',stroke=>'rgb(.3,.3,.3)');
foreach my $cor (@cors) {
    my $x = 5.0;
    my $y = 5.0;
    my $c = pop(@clrs);
    while ($x <= 795) {
        $x += $vx*$dt;
        $y += $vy*$dt + 0.5*$g*$dt*$dt;
        $vy += $g*$dt;
        if ($y >= 595) {
            $vy *= -$cor;
            $y = 595.0;
        }
        $svg->circle(cx=>$x,cy=>$y,r=>$r,stroke =>$c,fill=>"none",opacity =>  0.5);
    }
}
print $svg->xmlify;