I love these things!
[credits NIEHS kids page]
These are not animated:
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/illusion/images/wheels.gif')
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/illusion/images/spinner1.gif')
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/illusion/images/spinner3.gif')
Looking up or down?
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/illusion/images/image001.jpg')
How many black dots are there?
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/illusion/images/image002.jpg')
Stare at the black dot and the gray haze around it will appear to shrink.
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/illusion/images/image005.jpg')
Look for long enough and you'll see a giraffe
$this->handle_bbcode_img_match('http://www.niehs.nih.gov/kids/images/illusions/optgir.gif')
gotcha!