.student-notebook-page {
    --notebook-surface: color-mix(in srgb, var(--card-bg) 94%, var(--bg-main, #0f172a) 6%);
    --notebook-surface-strong: color-mix(in srgb, var(--card-bg) 88%, var(--bg-main, #0f172a) 12%);
    --notebook-input-surface: color-mix(in srgb, var(--input-bg, rgba(15, 23, 42, 0.6)) 92%, var(--bg-main, #0f172a) 8%);
    --notebook-muted-surface: color-mix(in srgb, var(--card-bg) 82%, transparent);
    --notebook-active-surface: color-mix(in srgb, var(--primary-soft, rgba(59, 130, 246, 0.12)) 52%, var(--card-bg) 48%);
    --notebook-border-strong: color-mix(in srgb, var(--border) 86%, rgba(255, 255, 255, 0.08));
    min-height: 100vh;
    background:
        radial-gradient(circle at top left, rgba(56, 189, 248, 0.18), transparent 28%),
        radial-gradient(circle at top right, rgba(244, 114, 182, 0.14), transparent 24%),
        var(--bg-grad);
}

.student-notebook-shell {
    width: min(1180px, calc(100% - 32px));
    margin: 0 auto;
    padding: 28px 0 48px;
}

.student-notebook-shell.hidden {
    display: none;
}

.student-notebook-loading {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-main);
}

.student-notebook-loading-card {
    width: min(420px, calc(100% - 32px));
    padding: 28px;
    border-radius: 24px;
    border: 1px solid var(--border);
    background: var(--card-bg);
    box-shadow: var(--shadow-md, 0 18px 50px rgba(15, 23, 42, 0.12));
    text-align: center;
}

.student-notebook-spinner {
    width: 42px;
    height: 42px;
    margin: 0 auto 14px;
    border-radius: 50%;
    border: 3px solid var(--border);
    border-top-color: var(--primary);
    animation: notebook-spin 1s linear infinite;
}

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

.student-notebook-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 24px 26px;
    margin-bottom: 18px;
}

.student-notebook-header h1 {
    margin: 0;
    font-size: clamp(1.8rem, 3vw, 2.35rem);
    line-height: 1.1;
}

.student-notebook-header p {
    margin: 8px 0 0;
    color: var(--text-sub);
    line-height: 1.55;
}

.student-notebook-chip-row {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 14px;
}

.student-notebook-chip {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border-radius: 999px;
    border: 1px solid var(--notebook-border-strong);
    background: var(--notebook-muted-surface);
    color: var(--text-main);
    font-size: 0.85rem;
    font-weight: 600;
}

.student-notebook-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: flex-end;
}

.student-notebook-layout {
    display: grid;
    grid-template-columns: minmax(280px, 340px) minmax(0, 1fr);
    gap: 18px;
}

.student-notebook-panel {
    border: 1px solid var(--border);
    border-radius: 24px;
    background: var(--card-bg);
    box-shadow: var(--shadow-md, 0 18px 50px rgba(15, 23, 42, 0.12));
    overflow: hidden;
}

.student-notebook-panel-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    padding: 18px 20px 14px;
    border-bottom: 1px solid var(--border);
}

.student-notebook-panel-head h2 {
    margin: 0;
    font-size: 1.08rem;
}

.student-notebook-panel-head p {
    margin: 6px 0 0;
    color: var(--text-sub);
    font-size: 0.88rem;
}

.student-notebook-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding: 16px;
    max-height: 70vh;
    overflow: auto;
}

.student-notebook-list-empty {
    padding: 24px 16px;
    border-radius: 18px;
    border: 1px dashed var(--notebook-border-strong);
    text-align: center;
    color: var(--text-sub);
    background: var(--notebook-muted-surface);
    line-height: 1.6;
}

.student-note-card {
    width: 100%;
    border: 1px solid var(--notebook-border-strong);
    border-radius: 18px;
    background: var(--notebook-surface-strong);
    color: var(--text-main);
    padding: 14px;
    text-align: left;
    cursor: pointer;
    transition: transform 0.16s ease, border-color 0.16s ease, box-shadow 0.16s ease;
}

.student-note-card:hover {
    transform: translateY(-1px);
    border-color: rgba(59, 130, 246, 0.35);
    box-shadow: 0 12px 28px rgba(15, 23, 42, 0.18);
}

.student-note-card.is-active {
    border-color: rgba(59, 130, 246, 0.5);
    box-shadow: 0 14px 28px rgba(59, 130, 246, 0.14);
    background: var(--notebook-active-surface);
}

.student-note-card-title {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    font-weight: 700;
    margin-bottom: 8px;
}

.student-note-card-time {
    color: var(--text-sub);
    font-size: 0.77rem;
    white-space: nowrap;
}

.student-note-card-preview {
    color: var(--text-sub);
    font-size: 0.88rem;
    line-height: 1.5;
    min-height: 2.7em;
    display: -webkit-box;
    -webkit-box-orient: vertical;
    -webkit-line-clamp: 2;
    overflow: hidden;
}

.student-note-editor {
    padding: 20px;
}

.student-note-form {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.student-note-meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    flex-wrap: wrap;
    color: var(--text-sub);
    font-size: 0.84rem;
}

.student-note-label {
    display: block;
    margin-bottom: 6px;
    font-weight: 700;
    color: var(--text-main);
}

.student-note-input,
.student-note-textarea {
    width: 100%;
    border-radius: 16px;
    border: 1px solid var(--notebook-border-strong);
    background: var(--notebook-input-surface);
    color: var(--text-main);
    padding: 14px 16px;
    font: inherit;
    box-sizing: border-box;
}

.student-note-input::placeholder,
.student-note-textarea::placeholder {
    color: color-mix(in srgb, var(--text-sub) 82%, transparent);
}

.student-note-input:focus,
.student-note-textarea:focus {
    outline: none;
    border-color: rgba(59, 130, 246, 0.65);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.16);
}

.student-note-textarea {
    min-height: 360px;
    line-height: 1.65;
    resize: vertical;
}

.student-note-counter {
    display: flex;
    justify-content: flex-end;
    color: var(--text-sub);
    font-size: 0.78rem;
    margin-top: 6px;
}

.student-note-toolbar {
    display: flex;
    justify-content: space-between;
    gap: 10px;
    flex-wrap: wrap;
    margin-top: 6px;
}

.student-note-toolbar-group {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.student-notebook-status {
    margin-top: 16px;
    min-height: 1.5em;
    font-size: 0.88rem;
    color: var(--text-sub);
}

.student-notebook-status[data-tone="success"] {
    color: var(--success);
}

.student-notebook-status[data-tone="error"] {
    color: var(--error);
}

.student-notebook-status[data-tone="saving"] {
    color: var(--primary);
}

.student-note-placeholder {
    border: 1px dashed var(--notebook-border-strong);
    border-radius: 18px;
    background: var(--notebook-muted-surface);
    padding: 22px;
    color: var(--text-sub);
    line-height: 1.65;
}

.student-note-placeholder[data-tone="error"] {
    border-style: solid;
    border-color: color-mix(in srgb, var(--error) 42%, var(--border));
    background: color-mix(in srgb, var(--danger-soft, rgba(239, 68, 68, 0.12)) 56%, var(--notebook-muted-surface) 44%);
    color: var(--text-main);
}

@media (max-width: 960px) {
    .student-notebook-shell {
        width: min(100% - 24px, 1180px);
        padding-top: 20px;
    }

    .student-notebook-layout {
        grid-template-columns: 1fr;
    }

    .student-notebook-list {
        max-height: none;
    }

    .student-note-textarea {
        min-height: 260px;
    }
}

@media (max-width: 640px) {
    .student-notebook-header {
        padding: 20px;
    }

    .student-notebook-actions,
    .student-note-toolbar {
        width: 100%;
        justify-content: stretch;
    }

    .student-notebook-actions .btn-outline,
    .student-notebook-actions .btn-primary,
    .student-note-toolbar-group .btn-outline,
    .student-note-toolbar-group .btn-primary,
    .student-note-toolbar-group .btn-secondary {
        width: 100%;
    }

    .student-note-toolbar-group {
        width: 100%;
    }
}