C2's library of shader effects is excellent, however it presents one major limitation - We cannot make an effect apply across multiple layers.
Let's assume we are making a game with a few parallaxed background layers and a few layers for the foreground - perhaps a lighting layer, layer for objects in front of player, etc.
This very common layout has a few very big problems when webGL effects come into the picture.
Let's consider the problem with layer-wide effects. Perhaps we want to adjust the HSL of the foreground and the background to simulate a night atmosphere. As Construct 2 is at the moment, we have to apply redundant effects to every single layer of the game in order to achieve this. This may not seem like such a problem, however it has huge performance ramifications that only really show their faces at high resolutions. I've done testing in a game with about 8-10 layers and having 10 layer effects is crippling in fullscreen, where the same game with a couple of layout effects runs very smoothly at the same resolution.
A nice way to fix this problem would be to let us have 'multi-layer' effects. Layout effects as-is are pretty much useless for any game with a UI as-is anyway, so that's not really a valid option.
Now, I would be very happy to find that there is a way to write my own shader that does this however I feel like this specific problem is hardcoded into the editor.
Thanks for listening! Let me know if you think this is an important subtle change.