HTML and CSS Reference
In-Depth Information
getBBox()
on the SVG flock element
<g id="flock">
. It will do all the heavy lift-
ing of calculating a box around the UFOs and return it to you as an object similar to
{ x:
20, y: 20, width: 325, height: 120 }
.
To summarize, the logic flows like this:
1
. Get the bounding box of the UFO flock.
2
. Check if they've hit a wall (if so increment their positions differently).
3
. Increment each x/y as appropriate and check if the player lost.
4
. Toggle animations.
5
. Potentially shoot.
Now, create your
update()
method to move UFOs in the flock with this code.
Listing 7.23. game.js—UFO movement AI
