Godot Camera shake without target

I’m working with godot 3.2 to make this screen shake, but my issue is that i don’t have a target, like in the example, in the example code, it’s a kinematic body that is being followed by the camera, i don’t have that, i’m making a match-three type of game, so i don’t use those.

What i tried it’s to use the main node, in which the game loop logic is executed but the camera shake didn’t work, also tried with another elementsd but it failed beacuse they are mostly HUD elements
and shows an error about global positions.

Also i not sure how to get the board/grid, since it’s instantiated by code.
How i can make shake camera without a target or get a similar effect?