first of all, after the “90deg” should follow at least 2 colors that will create the color gradient
you wrote “0” for the first color and “0” for the second color. writing just zero does not correspond to any color in CSS
of all the different ways to represent color in CSS, taught inside the “CSS Color Markers” section of the (New) Responsive Web Design course, writing zero will not output any color in CSS
also in this step 50, if you read what is requested with attention, at this point to solve this step is only asked to write “90deg” and in the next lessons the colors, to create the gradient, will be added
" First, in the .red CSS rule, set the background property to linear-gradient() , and pass it the value 90deg as the gradientDirection ."
also the solution to this step has been provided by @Cryptic_X in this same post
It is great that you solved the challenge, but instead of posting your full working solution, it is best to stay focused on answering the original poster’s question(s) and help guide them with hints and suggestions to solve their own issues with the challenge.
We are trying to cut back on the number of spoiler solutions found on the forum and instead focus on helping other campers with their questions and definitely not posting full working solutions.