Lesson 637 Basic Shapes

Was reviewing Lesson 637, Basic Shapes, and all the comments that follow. Left feeling a little confused on how to say "a square" (noun) vs. "square shaped" (adjective) as well as "a rectangle" (noun) vs." rectangular" (adjective) and similarly, "a triangle" (noun) vs. "triangular" (adjective). here are my guesses.

"a square" (noun): 一个 正方形

"square shaped" (adjective):正方形 的

"a rectangle" (noun): 一个长方形

"rectangular" (adjective):长方形 的

"a triangle" (noun): 一个三角形

"triangular" (adjective):三角形的

In the dialogue, is 方 的 just short for 长方形 的?

Thanks. AY