.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);

    font-family: var(--font-family-body);
    font-weight: 600;
    line-height: 1;
    text-decoration: none;
    white-space: nowrap;

    border: 1px solid transparent;
    cursor: pointer;
    user-select: none;

    transition: background-color var(--transition-fast),
                color var(--transition-fast),
                border-color var(--transition-fast),
                box-shadow var(--transition-fast),
                transform var(--transition-fast);
}

.btn:active,
.btn.is-pressed {
    transform: translateY(1px);
    filter: brightness(0.95);
}

.btn:disabled,
.btn.btn-disabled {
    opacity: 0.5;
    cursor: not-allowed;
    pointer-events: none;
}

.btn.btn-loading {
    cursor: progress;
    pointer-events: none;
    position: relative;
    color: transparent !important;
}

.btn.btn-loading::after {
    content: '';
    position: absolute;
    width: 16px;
    height: 16px;
    border: 2px solid currentColor;
    border-top-color: transparent;
    border-radius: 50%;
    animation: btn-spin 0.7s linear infinite;
}

.btn.btn-primary.btn-loading::after,
.btn.btn-secondary.btn-loading::after,
.btn.btn-danger.btn-loading::after {
    border: 2px solid #ffffff;
    border-top-color: transparent;
}

.btn.btn-outline.btn-loading::after,
.btn.btn-ghost.btn-loading::after {
    border: 2px solid var(--ink);
    border-top-color: transparent;
}

@keyframes btn-spin {
    to { transform: rotate(360deg); }
}

.btn-sm {
    height: 36px;
    padding: 0 14px;
    font-size: 14px;
    border-radius: 10px;
}

.btn-md {
    height: 44px;
    padding: 0 20px;
    font-size: var(--font-size-body);
    border-radius: var(--radius-md);
}

.btn-lg {
    height: 52px;
    padding: 0 24px;
    font-size: var(--font-size-body-lg);
    border-radius: 14px;
}

.btn-xl {
    height: 60px;
    padding: 0 32px;
    font-size: var(--font-size-h4);
    border-radius: var(--radius-lg);
}

.btn-primary {
    background: var(--accent);
    color: #ffffff;
    box-shadow: 0 4px 12px rgba(201, 110, 60, 0.22);
}

.btn-primary:hover {
    background: var(--accent-dark);
    color: #ffffff;
}

.btn-primary:focus-visible {
    box-shadow: 0 4px 12px rgba(201, 110, 60, 0.22),
                var(--focus-ring);
}

.btn-secondary {
    background: var(--primary);
    color: #ffffff;
}

.btn-secondary:hover {
    background: var(--primary-dark);
    color: #ffffff;
}

.btn-outline {
    background: var(--paper);
    color: var(--ink-strong);
    border: 1px solid var(--line-strong);
}

.btn-outline:hover {
    background: var(--bg);
    color: var(--ink-strong);
    border-color: var(--ink-muted);
}

.btn-outline-accent {
    background: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
    box-shadow: none;
}

.btn-outline-accent:hover {
    background: var(--accent-tint);
    color: var(--accent-dark);
    border-color: var(--accent-dark);
}

.btn-outline-accent:focus-visible {
    outline: none;
    box-shadow: var(--focus-ring);
}

.btn-ghost {
    background: transparent;
    color: var(--ink-strong);
}

.btn-ghost:hover {
    background: var(--primary-tint);
    color: var(--primary);
}

.btn-danger {
    background: var(--danger);
    color: #ffffff;
}

.btn-danger:hover {
    background: #8E2D24;
    color: #ffffff;
}

.btn-icon {
    padding: 0;
    aspect-ratio: 1 / 1;
}

.btn-icon.btn-sm  { width: 36px; }
.btn-icon.btn-md  { width: 44px; }
.btn-icon.btn-lg  { width: 52px; }
.btn-icon.btn-xl  { width: 60px; }