variant to solid, outlined, filled, text or link to choose how much paint a button uses, from the main call to action down to a plain link.color to default, primary or danger, and each color works with every variant.size to small, medium or large, with medium as the default.shape to round for a pill, or to circle with an icon and no label for a round icon button.block to make a button fill the width of its container, like the actions in a password reset email.icon role to draw a glyph beside the label, and iconPlacement="end" to put it after the text.