Hello. I'm trying to come up with an idea on how to make something on the map fade to transparent when the player walks behind it, similar to how Stardew Valley does it.

for example, if i walk behind a big tree, the tree would fade and become transparent so I can see myself behind the tree, but other players in the area would still see the fully opaque tree.

The only idea that comes to mind is using Crossed() and fading the tree using animate(), something like that. But then the tree would fade for everyone and not just the player walking behind it like intended.

Anyone have any ideas? Thanks a bunch!

You can use an image override to make things look different to different clients.
Is there somewhere I can read up on to help me accomplish that? I'm not super experienced here
In response to Anabellee
The usual first place to check on any built-in feature is the DM Reference, by hitting F1 in Dream Maker (or Help > Help On...). It's the most up-to-date source of information on everything that comes built-in.
I see the override variable there, I just don't know how to use it to make a tree go transparent only for the player walking behind it
In response to Anabellee
See the pages in the DM reference about images, the image proc, the images var for clients.

The point of /image is to attach them to atoms and display them to certain clients to make them appear. Kinda like HUDs, but anchored to objects on the map rather than positions in the screen.
// Create an image, set appearance and loc to the tree
var image/i = image(tree, tree) // see "image proc"

i.override = TRUE
animate(i, alpha = 100, time = 2)

// Show it to client
// (the client of the mob that just moved behind the tree)
client.images += i // see "images var (client)"

// Eventually...

// Hide it from client
client.images -= i

/image has a variable named "override" which causes the image to override/replace the appearance of the atom it's attached to, for the clients it's shown to.
Ah I see. I think I understand. Thank you very much for the help.