The Secret Diary has a sign-up form that also included validation, cookies, sessions, MySQL database, and Bootstrap.
You can check out the secret diary here and even log in if you want, though it is not secure and will not remember any diary inputs.
It will, however, validate (or invalidate) your information if you try to log in after signing up or use the wrong password.
This form, of course, is landing page type setup built in Bootstrap and is responsive, so it adjusts itself based on the size of the screen or browser window.
I created this page site in a course a full-stack web development course I took with Rob Percival.