Ghost/core/client/app/styles/patterns/buttons.css

/* Buttons
/* ---------------------------------------------------------- */

/* Base button style */
.btn {
    display: inline-block;
    margin-bottom: 0;
    padding: 9px 15px;
    border: #dfe1e3 1px solid;
    background: #fff;
    background-image: none; /* Reset unusual Firefox-on-Android default style; see https://github.com/necolas/normalize.css/issues/214 */
    border-radius: var(--border-radius);
    color: #808284;
    text-align: center;
    text-transform: uppercase;
    text-shadow: none;
    white-space: nowrap;
    letter-spacing: 1px;
    font-size: 1.1rem;
    line-height: 1.428571429;
    font-weight: 300;
    cursor: pointer;
    transition: color 0.2s ease,
    background 0.2s ease,
    border-color 0.2s ease;
}

/* When hovered or clicked */
.btn:hover,
.btn:focus {
    border-color: var(--blue);
    color: color(var(--blue) lightness(-10%));
    text-decoration: none;
}

/* When focused with keyboard */
.btn:focus,
.btn:active:focus,
.btn.active:focus {
    outline: thin dotted;
    outline: 0 auto -webkit-focus-ring-color;
    outline-offset: -2px;
}

/* When clicked */
.btn:active,
.btn.active {
    outline: 0;
    background-image: none;
    box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.2);
}

/* When disabled */
.btn.disabled,
.btn[disabled],
fieldset[disabled] .btn {
    box-shadow: none;
    opacity: 0.65;
    cursor: not-allowed;
    pointer-events: none;
}

.btn i {
    display: inline-block;
    vertical-align: middle;
}


/* Blue button
/* ---------------------------------------------------------- */

.btn-blue {
    border-color: color(var(--blue) lightness(-10%));
    background: var(--blue);
    color: #fff;
}

.btn-blue:hover,
.btn-blue:active,
.btn-blue:focus {
    border-color: color(var(--blue) lightness(-20%));
    background: color(var(--blue) lightness(-10%));
    color: #fff;
}


/* Green button
/* ---------------------------------------------------------- */

.btn-green {
    border-color: color(var(--green) lightness(-10%));
    background: var(--green);
    color: #fff;
}

.btn-green:hover,
.btn-green:active,
.btn-green:focus {
    border-color: color(var(--green) lightness(-20%));
    background: color(var(--green) lightness(-10%));
    color: #fff;
}


/* Red button
/* ---------------------------------------------------------- */

.btn-red {
    border-color: color(var(--red) lightness(-10%));
    background: var(--red);
    color: #fff;
}

.btn-red:hover,
.btn-red:active,
.btn-red:focus {
    border-color: color(var(--red) lightness(-20%));
    background: color(var(--red) lightness(-10%));
    color: #fff;
}


/* Link button
/* ---------------------------------------------------------- */

/* For styling a button like a link */
.btn-link {
    border-color: transparent;
    background: transparent;
    color: var(--blue);
}

.btn-link:hover,
.btn-link:active,
.btn-link:focus {
    border-color: transparent;
    background: transparent;
    color: var(--blue);
    text-decoration: underline;
}

.btn-link.disabled,
.btn-link[disabled] {
    box-shadow: none;
    color: #b2b2b2;
    opacity: 0.65;
    cursor: not-allowed;
    pointer-events: none;
}


/* Minor button
/* ---------------------------------------------------------- */

/* For buttons with a small/insignificant action for
// example a "cancel" button. Style is de-emphasised. */
.btn-minor {
    padding: 8px 15px;
    text-transform: none;
    letter-spacing: 0;
    font-size: 1.2rem;
}

.btn-minor:hover,
.btn-minor:active,
.btn-minor:focus {
    border-color: #c1c1c1;
    background: #fff;
    box-shadow: none;
    color: #808284;
}


/* Button size variations
/* ---------------------------------------------------------- */

.btn-lg {
    padding: 12px 18px;
    border-radius: 4px;
    font-size: 1.4rem;
    line-height: 1.33;
}

.btn-sm {
    padding: 7px 10px;
    border-radius: 2px;
    font-size: 1rem;
    line-height: 1.5;
}

.btn-block {
    display: block;
    width: 100%;
}

/* Vertically space out multiple block buttons */
.btn-block + .btn-block {
    margin-top: 5px;
}

/* Specificity overrides */
input[type="submit"].btn-block,
input[type="reset"].btn-block,
input[type="button"].btn-block {
    width: 100%;
}

/* Spin Buttons!
/* ---------------------------------------------------------- */
.spinner {
    position: relative;
    display: inline-block;
    box-sizing: border-box;
    margin: -2px 0;
    width: 14px;
    height: 14px;
    border: rgba(0,0,0,0.2) solid 4px;
    border-radius: 100px;
    animation: spin 1s linear infinite;
}

.spinner:before {
    content: "";
    display: block;
    margin-top: 6px;
    width: 4px;
    height: 4px;
    background: rgba(0,0,0,0.6);
    border-radius: 100px;
}