You made a typing error in the Basic CSS course:
https://learn.freecodecamp.org/responsive-web-design/basic-css/use-css-variables-to-change-several-elements-at-once
You ask for three times adjusting the --penguin-skin, but i assume you meant --penguin-skin, --penguin-belly and --penguin-beak, cause the task was complete when i did just that.