.pc-premium-shell {
    background: linear-gradient(
        180deg,
        color-mix(in srgb, var(--color-surface) 96%, var(--color-primary) 4%),
        var(--color-bg)
    );
}

.pc-premium-panel {
    border: 1px solid color-mix(in srgb, var(--color-border) 84%, transparent);
    background: color-mix(in srgb, var(--color-surface) 96%, white 4%);
    box-shadow: 0 18px 50px rgba(15, 23, 42, 0.08);
}

.dark .pc-premium-panel {
    background: color-mix(in srgb, var(--color-surface) 92%, black 8%);
    box-shadow: 0 18px 50px rgba(0, 0, 0, 0.25);
}

.pc-segment {
    border: 1px solid color-mix(in srgb, var(--color-border) 86%, transparent);
    background: color-mix(in srgb, var(--color-bg) 88%, var(--color-surface) 12%);
    padding: 5px;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.42);
}

.pc-tab-btn,
.pc-segment-btn {
    min-height: 44px;
    border-radius: 10px;
    transition: background-color .18s ease, border-color .18s ease, color .18s ease, box-shadow .18s ease, transform .18s ease;
}

.pc-segment-btn {
    border: 1px solid transparent;
}

.calc-type-btn {
    position: relative;
    min-height: 96px;
    overflow: hidden;
}

.calc-type-btn > div:first-child {
    display: flex;
    align-items: center;
    gap: 8px;
    letter-spacing: 0;
}

.calc-type-btn > div:first-child::before {
    display: inline-flex;
    width: 30px;
    height: 30px;
    align-items: center;
    justify-content: center;
    border-radius: 9px;
    background: color-mix(in srgb, currentColor 12%, transparent);
    font-family: "Font Awesome 5 Free";
    font-size: 12px;
    font-weight: 900;
}

#btnPermutation > div:first-child::before {
    content: "\f362";
}

#btnCombination > div:first-child::before {
    content: "\f0c0";
}

.calc-type-btn::after {
    content: "";
    position: absolute;
    top: 14px;
    right: 14px;
    width: 8px;
    height: 8px;
    border-radius: 999px;
    background: color-mix(in srgb, var(--color-text-light) 38%, transparent);
    box-shadow: 0 0 0 4px color-mix(in srgb, var(--color-text-light) 8%, transparent);
}

.pc-segment-btn.btn-toggle-active {
    background:
        linear-gradient(135deg, color-mix(in srgb, var(--color-primary) 94%, white 6%), color-mix(in srgb, var(--color-secondary) 84%, var(--color-primary) 16%));
    border-color: color-mix(in srgb, var(--color-primary) 70%, transparent);
    color: white;
    box-shadow: 0 16px 34px color-mix(in srgb, var(--color-primary) 28%, transparent);
    transform: translateY(-1px);
}

.pc-segment-btn.btn-toggle-active::after {
    background: white;
    box-shadow: 0 0 0 4px rgba(255, 255, 255, 0.22), 0 0 18px rgba(255, 255, 255, 0.8);
}

.pc-segment-btn.btn-toggle-active > div,
.pc-segment-btn.btn-toggle-active > div:first-child::before {
    color: white;
}

.pc-segment-btn.btn-toggle-inactive {
    background: color-mix(in srgb, var(--color-surface) 96%, white 4%);
    border-color: color-mix(in srgb, var(--color-border) 78%, transparent);
    color: var(--color-text-medium);
}

.pc-segment-btn.btn-toggle-inactive > div:first-child {
    color: var(--color-text-dark);
}

.pc-segment-btn.btn-toggle-inactive > div:last-child {
    color: var(--color-text-medium);
}

.pc-segment-btn.btn-toggle-inactive:hover {
    border-color: color-mix(in srgb, var(--color-primary) 46%, var(--color-border));
    background: color-mix(in srgb, var(--color-primary) 5%, var(--color-surface));
    color: var(--color-text-dark);
    box-shadow: 0 10px 24px rgba(15, 23, 42, 0.07);
    transform: translateY(-1px);
}

.pc-tab-btn-active {
    background: var(--color-surface);
    color: var(--color-primary);
    box-shadow: 0 8px 22px rgba(15, 23, 42, 0.08);
}

.pc-tab-btn {
    color: var(--color-text-medium);
}

.tool-input-group {
    border: 1px solid color-mix(in srgb, var(--color-border) 76%, transparent);
    border-radius: 16px;
    background: color-mix(in srgb, var(--color-surface) 92%, var(--color-bg) 8%);
    padding: 14px;
    transition: border-color .18s ease, box-shadow .18s ease, background-color .18s ease;
}

.tool-input-group:focus-within {
    border-color: color-mix(in srgb, var(--color-primary) 62%, var(--color-border));
    background: var(--color-surface);
    box-shadow: 0 14px 32px color-mix(in srgb, var(--color-primary) 12%, transparent);
}

.pc-premium-panel .tool-input {
    min-height: 48px;
    width: 100%;
    border: 1px solid color-mix(in srgb, var(--color-border) 82%, transparent);
    border-radius: 12px;
    background: color-mix(in srgb, var(--color-surface) 94%, white 6%);
    color: var(--color-text-dark);
    font-size: 15px;
    font-weight: 650;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.5);
    transition: border-color .18s ease, box-shadow .18s ease, background-color .18s ease;
}

.pc-premium-panel .tool-input::placeholder {
    color: color-mix(in srgb, var(--color-text-light) 78%, transparent);
    font-weight: 500;
}

.pc-premium-panel .tool-input:hover {
    border-color: color-mix(in srgb, var(--color-primary) 34%, var(--color-border));
}

.pc-premium-panel .tool-input:focus {
    border-color: var(--color-primary);
    outline: none;
    box-shadow: 0 0 0 4px color-mix(in srgb, var(--color-primary) 14%, transparent);
}

.pc-premium-panel input[type="number"].tool-input {
    font-size: 18px;
    font-weight: 800;
}

.pc-answer-value {
    overflow-wrap: anywhere;
    line-height: 1.08;
}

.pc-solution-list {
    list-style: none;
    counter-reset: solution-step;
    padding: 0;
    margin: 0;
}

.pc-solution-list li {
    counter-increment: solution-step;
    display: grid;
    grid-template-columns: 32px 1fr;
    gap: 12px;
    padding: 14px 0;
    border-bottom: 1px solid var(--color-border);
}

.pc-solution-list li::before {
    content: counter(solution-step);
    display: inline-flex;
    width: 32px;
    height: 32px;
    align-items: center;
    justify-content: center;
    border-radius: 999px;
    background: color-mix(in srgb, var(--color-primary) 12%, transparent);
    color: var(--color-primary);
    font-size: 12px;
    font-weight: 800;
}

.pc-solution-list li:last-child {
    border-bottom: 0;
}

.mode-selection-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
    width: 100%;
    text-align: left;
}

@media (min-width: 768px) {
    .mode-selection-grid {
        grid-template-columns: repeat(4, minmax(0, 1fr));
    }
}

.mode-card {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    text-align: left;
    padding: 16px;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: 14px;
    transition: border-color .18s ease, background-color .18s ease, box-shadow .18s ease, transform .18s ease;
    cursor: pointer;
    width: 100%;
    min-height: 116px;
}

.mode-card:hover:not(.mode-card-disabled) {
    border-color: var(--color-primary);
    background-color: color-mix(in srgb, var(--color-primary) 8%, var(--color-surface));
    transform: translateY(-2px);
    box-shadow: 0 12px 30px rgba(15, 23, 42, 0.08);
}

.mode-card-active {
    border-color: var(--color-primary);
    background: color-mix(in srgb, var(--color-primary) 10%, var(--color-surface));
    box-shadow: inset 0 0 0 1px var(--color-primary);
}

.mode-card-disabled {
    opacity: .48;
    cursor: not-allowed;
    filter: grayscale(1);
}

.mode-card-title {
    display: block;
    margin-bottom: 4px;
    color: var(--color-text-dark);
    font-size: 14px;
    font-weight: 800;
}

.mode-card-desc {
    display: block;
    color: var(--color-text-medium);
    font-size: 12px;
    line-height: 1.45;
}

.mode-badge-permutation-only {
    display: inline-block;
    margin-top: auto;
    padding: 3px 7px;
    border-radius: 999px;
    background: color-mix(in srgb, var(--color-error) 10%, transparent);
    color: var(--color-error);
    font-size: 9px;
    font-weight: 800;
    text-transform: uppercase;
}