Tip Calculator App

It looks close to the design and functionalities works as supposed to, well done!

My suggestions:

• Style of select tip buttons doesn't reset after focusing out. Instead of changing background with JavaScript, you can use focus selector with CSS like button:focus {style}
• Decimals overflows on certain calculations. You can use .toFixed(number) method to prevent that.
• Error for input 0 doesn't refresh on correct input. You can add an else state for inputs more than 0.

Accessibility:

• You can change bill heading from <h2> to <h1>. Even though they look to have same importance, for SEO it's still better solution than not using <h1>. However for this project if you won't mind the time another approach would be: Instead of using provided logo.svg you can use <h1>splitter<h1/> and style as logo is just a text.