Disabled inputs
Add the disabled attribute to <input> or <button> buttons to prevent user input and trigger a slightly different look.
Add the .disabled class to <a> buttons;
Be aware: adding the .disabled class to elements is purely a stylistic helper state, actually making the element not respond to interactions from mouse click, touches and text activations needs to be handled with JavaScript.
Contextual styles
Use any of the available .action-* button classes to highlight primary actions or convey the positive or dangerous nature of an action.