The structure of a level is the following:
level: main container
level-leftfor the left side. This element is required, even if it is empty
level-rightfor the right side
level-itemfor each individual element
level-item, you can then insert almost anything you want: a title, a button, a text input, or just simple text. No matter what elements you put inside a Bulma
level, they will always be vertically centered.