body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f3f4f6;
    color: #1f2937;
    margin: 0;
    overflow: hidden;
    height: 100vh;
}

/* --- Navigation & Tabs --- */
.main-tab-btn {
    background: rgba(255, 255, 255, 0.1);
    border: none;
    color: white;
    padding: 8px 20px;
    font-weight: 600;
    font-size: 14px;
    cursor: pointer;
    border-radius: 8px 8px 0 0;
    transition: all 0.2s;
}

.main-tab-btn.active {
    background: #fff;
    color: #0ea5e9;
}

/* --- Sidebar --- */
.sidebar {
    width: 260px;
    background-color: #ffffff;
    border-right: 1px solid #e5e7eb;
    overflow-y: auto;
    flex-shrink: 0;
}

.sidebar-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 20px;
    color: #4b5563;
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    border-bottom: 1px solid #f3f4f6;
    cursor: pointer;
    transition: all 0.2s;
}

.sidebar-item:hover {
    background-color: #f9fafb;
    color: #0ea5e9;
}

.sidebar-item.active {
    background-color: #f0f9ff;
    color: #0ea5e9;
    border-right: 3px solid #0ea5e9;
}

/* --- Kana Cards --- */
.kana-card {
    background: white;
    border: 1px solid #e5e7eb;
    height: 110px;
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.kana-card:hover {
    transform: translateY(-2px);
    border-color: #0ea5e9;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

.kana-card.active {
    background-color: #0ea5e9;
    border-color: #0ea5e9;
    color: white;
}

.kana-char {
    font-size: 32px;
    font-weight: 700;
}

.kana-romaji {
    font-size: 11px;
    margin-top: 4px;
    color: #9ca3af;
    font-weight: 600;
    text-transform: uppercase;
}

.kana-card.active .kana-romaji {
    color: rgba(255, 255, 255, 0.8);
}

/* --- Detail Panel --- */
.detail-panel {
    width: 420px;
    background-color: white;
    border-left: 1px solid #e5e7eb;
    display: flex;
    flex-direction: column;
    padding: 24px;
    overflow-y: auto;
}

.detail-panel.is-hidden {
    display: none;
}

.detail-section-title {
    padding: 8px 16px;
    background-color: #f1f5f9;
    text-transform: uppercase;
    font-size: 10px;
    font-weight: 800;
    color: #64748b;
    letter-spacing: 0.1em;
    border-radius: 6px;
    margin-top: 24px;
}

.detail-section-title:first-child {
    margin-top: 0;
}

.pronunciation-box {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px;
    background: #f8fafc;
    border-radius: 16px;
    margin-top: 8px;
}

.stroke-box {
    aspect-ratio: 1;
    background: #f8fafc;
    border: 1px solid #f1f5f9;
    border-radius: 16px;
    position: relative;

.detail-section-title {
    padding: 8px 16px;
    background-color: #f1f5f9;
    text-transform: uppercase;
    font-size: 10px;
    font-weight: 800;
    color: #64748b;
    letter-spacing: 0.1em;
    border-radius: 6px;
    margin-top: 24px;
}

.detail-section-title:first-child {
    margin-top: 0;
}

.pronunciation-box {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px;
    background: #f8fafc;
    border-radius: 16px;
    margin-top: 8px;
}

.stroke-box {
    aspect-ratio: 1;
    background: #f8fafc;
    border: 1px solid #f1f5f9;
    border-radius: 16px;
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-top: 8px;
}

/* --- Utilities --- */
.no-scrollbar::-webkit-scrollbar {
    display: none;
}
.no-scrollbar {
    -ms-overflow-style: none;
    scrollbar-width: none;
}

@media (max-width: 1024px) {
    .sidebar {
        position: fixed;
        left: -100%;
        top: 0;
        bottom: 0;
        z-index: 50;
        transition: left 0.3s ease;
    }

    .sidebar.open {
        left: 0;
    }

    .detail-panel {
        position: fixed;
        right: -100%;
        top: 0;
        bottom: 0;
        z-index: 40;
        transition: right 0.3s ease;
        width: 100%;
    }

    .detail-panel.is-hidden {
        display: none;
    }

    .detail-panel.open {
        right: 0;
    }
}

@media (max-width: 640px) {
    .kana-card {
        height: 90px;
    }
    .kana-char {
        font-size: 24px;
    }
}