Tip calculator

This is my first "Junior" challenge, after 3 to 4 months studying web development. It took me like two nights to finish it. I ended up improvising a lot of things and I'm not sure if this is the right way. For example, the entire session of the "tip %" buttons, the javascript of the input fields and also all the rest of the javascript.

On the CSS, I tried to make it as close to the reference as possible (both desktop and mobile) trying to style things as little as possible.

About HTML, I used some tags that I don't know how relevant or convenient they are, like <output>, <section> and <label> ("button" and "text" of the tipping session).

I think the code is a little messy.

I will appreciate any feedback. Thank You!