:root {
    /* ---------- App shell ---------- */
    --shell-max-width: min(1680px, calc(100vw - clamp(24px, 3vw, 64px)));
    --sidebar-width: clamp(248px, 16vw, 280px);
    --content-pad-x: clamp(16px, 2vw, 32px);
    --content-pad-y: clamp(18px, 2.2vw, 36px);
    /* ---------- Radius ---------- */
    --radius-sm: clamp(10px, 0.7vw, 12px);
    --radius-md: clamp(14px, 1vw, 18px);
    --radius-lg: clamp(18px, 1.4vw, 24px);
    --radius-pill: 999px;
    /* ---------- Type scale ---------- */
    --fs-body: clamp(14px, 0.22vw + 13px, 16px);
    --fs-small: clamp(12px, 0.15vw + 11px, 14px);
    --fs-label: clamp(11px, 0.12vw + 10px, 13px);
    --fs-title-sm: clamp(18px, 0.5vw + 16px, 24px);
    --fs-title-md: clamp(24px, 1vw + 18px, 36px);
    --fs-title-lg: clamp(32px, 1.6vw + 20px, 56px);
    /* ---------- Spacing ---------- */
    --space-1: clamp(6px, 0.35vw, 8px);
    --space-2: clamp(10px, 0.5vw, 12px);
    --space-3: clamp(14px, 0.8vw, 18px);
    --space-4: clamp(18px, 1vw, 24px);
    --space-5: clamp(24px, 1.3vw, 32px);
    --space-6: clamp(28px, 1.8vw, 40px);
    /* ---------- Controls ---------- */
    --btn-h-sm: clamp(40px, 2.5vw, 46px);
    --btn-h-md: clamp(46px, 3vw, 58px);
    --icon-sm: clamp(28px, 2vw, 34px);
    --icon-md: clamp(36px, 2.5vw, 44px);
    --avatar-card: clamp(72px, 5vw, 92px);
    /* ---------- Shadows ---------- */
    --shadow-soft: 0 10px 24px rgba(15,23,42,0.08);
    --shadow-card: 0 12px 28px rgba(15,23,42,0.10);
    --shadow-strong: 0 16px 36px rgba(15,23,42,0.14);


    --bg: #EEF4FB; /* light blue background like screenshot */
    --sidebar-bg: #FFFFFF;
    --border: #E6EAF0;
    --text: #0F172A;
    --muted: #64748B;
    --active-bg: #E9FBF6; /* mint highlight like "My Classes" */
    --active-text: #0AA189;
    --shadow: 0 10px 24px rgba(15, 23, 42, 0.08);
    --radius: 18px;
}

body.teacher-shell {
    margin: 0;
    background: var(--bg);
    font-size: var(--fs-body);
}

.app-shell {
    display: flex;
    min-height: 100vh;
}

.sidebar {
    width: var(--sidebar-width);
    background: var(--sidebar-bg);
    border-right: 1px solid var(--border);
    display: flex;
    flex: 0 0 var(--sidebar-width);
}

.sidebar-inner {
    width: 100%;
    display: flex;
    flex-direction: column;
}

.sidebar-logo {
    padding: var(--space-4) var(--space-4) var(--space-3);
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: center;
}

    .sidebar-logo img {
        max-width: clamp(96px, 8vw, 126px);
        height: auto;
    }

.sidebar-user {
    display: flex;
    gap: var(--space-2);
    align-items: center;
    padding: var(--space-4);
    border-bottom: 1px solid var(--border);
}

.sidebar-avatar {
    width: var(--icon-md);
    height: var(--icon-md);
    border-radius: 999px;
    background: #00BFA6;
    color: #fff;
    display: grid;
    place-items: center;
    font-weight: 800;
    font-size: clamp(14px, 0.35vw + 12px, 18px);
}

.sidebar-user-hello {
    font-weight: 800;
    color: var(--text);
    font-size: var(--fs-body);
}

.sidebar-user-name {
    color: var(--muted);
    font-size: var(--fs-small);
    margin-top: 1px;
}

.sidebar-nav {
    padding: var(--space-3);
    display: flex;
    flex-direction: column;
    gap: var(--space-1);
}

.sidebar-link {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: clamp(10px, 0.8vw, 14px) clamp(12px, 1vw, 16px);
    border-radius: var(--radius-md);
    text-decoration: none;
    color: #334155;
    font-size: var(--fs-body);
}

    .sidebar-link:hover {
        background: rgba(15, 23, 42, 0.04);
    }

    .sidebar-link.active {
        background: var(--active-bg);
        color: var(--active-text);
        font-weight: 700;
    }

.sidebar-ico {
    width: 28px;
    display: inline-flex;
    justify-content: center;
    color: inherit;
}

.sidebar-section {
    margin: var(--space-4) var(--space-2) var(--space-2);
    font-size: var(--fs-label);
    letter-spacing: .12em;
    color: #94A3B8;
    font-weight: 800;
}

.sidebar-bottom {
    margin-top: auto;
    padding: var(--space-3);
    border-top: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    gap: var(--space-1);
}

.sidebar-link.logout {
    color: #E11D48;
}

    .sidebar-link.logout:hover {
        background: rgba(225, 29, 72, 0.08);
    }

/* Main content */
.main-content {
    flex: 1;
    min-width: 0;
    padding: var(--content-pad-y) var(--content-pad-x);
    background: radial-gradient(1200px 700px at 15% 10%, rgba(255,255,255,0.85), rgba(255,255,255,0) 60%), radial-gradient(1000px 700px at 65% 30%, rgba(255,255,255,0.7), rgba(255,255,255,0) 60%), var(--bg);
}

.content-wrap {
    width: 100%;
    max-width: var(--shell-max-width);
}