You will forget what your original vision is when you get lost in implementation details. So it's important to record that up front. The most important part is the feeling behind the application you want to build.
Generate 2-3 different HTML file experiments based on the initial idea to get the brain cooking and explore different directions.
Note: This is an example of a highlighted content box styled like a quote with a thick left border only.
Testing different states and variations of the form elements.