Learn Polish: Widać tylko sam wierzchołek tego drzewa. - You can only see the very top of this tree.

When placed directly before a noun like wierzchołek (top) and paired with a restrictive word like tylko (only), sam acts as an intensifying modifier. It means "the very" or "nothing but", emphasizing that absolutely nothing else is visible.

What case is sam wierzchołek in after widać?

It is in the accusative case. The word widać (one can see / it is visible) takes a direct object in the accusative. Because wierzchołek is a masculine inanimate noun, its accusative form looks identical to its nominative form, and the modifier sam matches it perfectly.

There is no word for "you" in the Polish sentence. How does widać work here?

Widać is a special impersonal word that translates to "it can be seen" or "one can see". Polish strongly prefers these subjectless constructions over literally translating the English general "you" when making statements about what is visible or possible.

Why is the end of the sentence tego drzewa?

This is the genitive case, used here to show a relationship equivalent to the English "of". It connects the top to the tree, literally translating to "of this tree" (the nominative neuter phrase to drzewo becomes tego drzewa).