Can you implement the following?

1. Checkbox Container: Make a container change background color when its checkbox is checked. (Easy mode, you can find the answer somewhere in the last section.)
2. Form Validation Feedback: Create a form field container that shows different colors for valid/invalid states
3. Conditional Content: Build a survey question that reveals follow-up content based on radio button selection
4. Multi-Element Response: Design a contact form container that responds differently to text inputs vs textareas
5. Complex Attribute Targeting: Create a file upload zone that responds to both focus states and file type attributes

The solutions can be found here.