/* Fluent 2 button system. Class contract (.app-btn, variants) is stable. */
.app-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    height: var(--control-height-md);
    padding-inline: var(--spacing-md);
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    font-size: var(--font-size-button);
    font-weight: var(--font-weight-medium);
    line-height: 1;
    white-space: nowrap;
    cursor: pointer;
    user-select: none;
    transition:
        background-color var(--transition-fast),
        border-color var(--transition-fast),
        color var(--transition-fast),
        box-shadow var(--transition-fast);
}

.app-btn:disabled,
.app-btn[aria-disabled="true"] {
    background: var(--color-background-muted);
    border-color: var(--color-border-default);
    color: var(--color-text-disabled);
    opacity: 1;
    cursor: not-allowed;
    box-shadow: none;
}

.app-btn:focus-visible {
    box-shadow: var(--focus-ring);
}

.app-btn:active:not(:disabled) {
    transform: scale(0.98);
}

.app-btn--primary {
    background: var(--btn-primary-bg);
    color: var(--btn-primary-fg);
}

.app-btn--primary:hover:not(:disabled) {
    background: var(--btn-primary-hover);
}

.app-btn--primary:active:not(:disabled) {
    background: var(--color-action-primary-pressed);
}

.app-btn--secondary,
.app-btn--outline,
.app-btn--search,
.app-btn--print,
.app-btn--export,
.app-btn--refresh,
.app-btn--close,
.app-btn--edit {
    background: var(--color-background-surface);
    border-color: var(--color-border-default);
    color: var(--color-text-primary);
}

.app-btn--secondary:hover:not(:disabled),
.app-btn--outline:hover:not(:disabled),
.app-btn--search:hover:not(:disabled),
.app-btn--print:hover:not(:disabled),
.app-btn--export:hover:not(:disabled),
.app-btn--refresh:hover:not(:disabled),
.app-btn--close:hover:not(:disabled),
.app-btn--edit:hover:not(:disabled) {
    background: var(--color-hover);
    border-color: var(--color-border-strong);
}

.app-btn--subtle,
.app-btn--ghost {
    background: transparent;
    border-color: transparent;
    color: var(--color-text-primary);
}

.app-btn--subtle:hover:not(:disabled),
.app-btn--ghost:hover:not(:disabled) {
    background: var(--color-hover);
}

.app-btn--save,
.app-btn--add {
    background: var(--btn-success-bg);
    color: var(--btn-success-fg);
}

.app-btn--save:hover:not(:disabled),
.app-btn--add:hover:not(:disabled) {
    background: var(--btn-success-hover);
}

.app-btn--delete,
.app-btn--danger {
    background: var(--color-background-surface);
    border-color: color-mix(in srgb, var(--color-status-danger) 55%, var(--color-border-default));
    color: var(--color-status-danger);
}

.app-btn--delete:hover:not(:disabled),
.app-btn--danger:hover:not(:disabled) {
    background: var(--btn-danger-fill);
    border-color: var(--btn-danger-fill);
    color: var(--btn-danger-fg);
}

.app-btn--sm,
.app-btn--icon {
    height: var(--control-height-sm);
    padding-inline: var(--spacing-sm);
    font-size: var(--font-size-grid);
}

.app-btn--icon {
    width: var(--control-height-sm);
    padding-inline: 0;
}

.app-btn--lg {
    height: var(--control-height-lg);
    padding-inline: var(--spacing-lg);
    font-size: var(--font-size-section-title);
}

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

.app-btn.is-loading {
    pointer-events: none;
    position: relative;
}

.app-btn.is-loading .app-btn__label,
.app-btn.is-loading .app-icon {
    visibility: hidden;
}

.app-btn.is-loading::after {
    content: "";
    position: absolute;
    width: 14px;
    height: 14px;
    border: 2px solid currentColor;
    border-block-start-color: transparent;
    border-radius: 50%;
    animation: app-btn-spin 0.6s linear infinite;
}

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

@media (prefers-reduced-motion: reduce) {
    .app-btn:active:not(:disabled) {
        transform: none;
    }

    .app-btn.is-loading::after {
        animation: none;
        border-block-start-color: currentColor;
    }
}

.app-btn--primary:disabled,
.app-btn--save:disabled,
.app-btn--add:disabled,
.app-btn--delete:disabled,
.app-btn--danger:disabled,
.app-btn--secondary:disabled,
.app-btn[aria-disabled="true"] {
    background: var(--color-background-muted);
    border-color: var(--color-border-default);
    color: var(--color-text-disabled);
}