v20.1 Terrain Backdrop Change 1.1

This is a simple plugin that changes the backdrop when a terrain is activated and reverts it to what it was at the start of the battle when that terrain ends. This only affects backdrops and not bases. You could easily modify it to include those though!

Please note: You need to provide your own backdrops. You should have 4 in total:
"electric_bg"
"grassy_bg"
"misty_bg"
"psychic_bg"
Place these graphics in Graphics/Battlebacks

There is a version for v19.1 and one for v20.1. Both are tested. Only use one!

This is my first time making a plugin, so if there are any issues, let me know!