HTML and CSS Reference
Until Opera comes up with a fix, using getBBox() on an SVG element in Opera won't
work as expected.
Step 4: Make the UFOs randomly shoot
Each time your update() method is called, a shot might be fired based on a random
number check. If a UFO does shoot, you're going to use a piece of the bounding box you
generated in the previous listing to fire from one of the bottom-row UFOs. You could make
the firing more dynamic, such as only from the bottom row of each column, but that takes a
lot more logic, and this way you can use the SVG bounding box data again to speed things
up. Integrate the following listing to make your UFOs fire lasers.