The default code that gets loaded when a new effect is created has some pretty bad code for generating the coordinates. It generates coordinates in the range 0..1 on both axes, no matter the size of the window. This causes effects to be stretched in one direction or another under most circumstances.
As this is rarely if ever desired, it should be replaced with a better line, saving people the work of replacing it themselves when they notice their effects look wrong in another browser window.
This generates coordinates in the range -1..1 on the larger axis, and less on the other. If you want a 0..1 range on the larger axis, this should work, but this is less useful as it is hard to center anything:
The default code that gets loaded when a new effect is created has some pretty bad code for generating the coordinates. It generates coordinates in the range 0..1 on both axes, no matter the size of the window. This causes effects to be stretched in one direction or another under most circumstances.
As this is rarely if ever desired, it should be replaced with a better line, saving people the work of replacing it themselves when they notice their effects look wrong in another browser window.
I suggest the following:
This generates coordinates in the range -1..1 on the larger axis, and less on the other. If you want a 0..1 range on the larger axis, this should work, but this is less useful as it is hard to center anything: