Seville

Bold and modernistic with opposing rounded corners and opposing square corners such that the button resembles a Seville orange, rounded in shape, sharp in taste.

Seville large left-aligned anchor

Change what the button says:

HTML

<div class="html_button btn-left">
    <a href="#" class="btn seville large">Your button text here</a>
</div>

CSS

.seville {
    background:white;
    padding:1em 2em;
    border:0.4em solid black;
    border-radius:2em 0 2em 0;
    color:black;
    font-weight:bold;
    transition:0.1s;
    opacity:1;
}
.seville:hover {
    background:black;
    color:white;
    transition:0.1s;
}

Check out the docs for a full installation and how-to guide for HTML Buttons.