.physics-lesson {
    --bg: #f7fafc;
    --card: #ffffff;
    --accent: #0066cc;
    --muted: #6b7280;
    --glass: rgba(255,255,255,0.6);
    font-family: Inter, system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial;
    color: #0f172a;
}

    .physics-lesson * {
        box-sizing: border-box
    }

    .physics-lesson.wrap {
        max-width: 980px;
        margin: 28px auto;
        padding: 20px;
        background: linear-gradient(180deg,#f2f8ff 0%,var(--bg) 100%);
    }

    .physics-lesson header {
        display: flex;
        gap: 16px;
        align-items: center
    }

    .physics-lesson .logo {
        width: 56px;
        height: 56px;
        border-radius: 12px;
        background: linear-gradient(135deg,var(--accent),#3b82f6);
        display: grid;
        place-items: center;
        color: white;
        font-weight: 700;
        font-size: 20px
    }

    .physics-lesson h1 {
        margin: 0 0 6px 0;
        font-size: 22px
    }

    .physics-lesson p.lead {
        margin: 0;
        color: var(--muted)
    }

    .physics-lesson .grid {
        display: grid;
        grid-template-columns: 1fr 360px;
        gap: 18px;
        margin-top: 18px
    }

@media(max-width:900px) {
    .physics-lesson .grid {
        grid-template-columns: 1fr
    }

    .physics-lesson .toc {
        order: -1
    }
}

.physics-lesson .card {
    background: var(--card);
    border-radius: 12px;
    padding: 18px;
    box-shadow: 0 6px 18px rgba(15,23,42,0.06)
}

.physics-lesson .section {
    margin-bottom: 14px
}

    .physics-lesson .section h2 {
        font-size: 18px;
        margin: 0 0 8px 0
    }

.physics-lesson .small {
    color: var(--muted);
    font-size: 14px
}

.physics-lesson .toc {
    position: sticky;
    top: 20px;
    align-self: start
}

    .physics-lesson .toc h3 {
        margin: 0 0 10px 0
    }

    .physics-lesson .toc ul {
        padding: 0;
        margin: 0;
        list-style: none
    }

    .physics-lesson .toc li {
        margin: 8px 0
    }

.physics-lesson .btn {
    display: inline-flex;
    gap: 8px;
    align-items: center;
    padding: 8px 12px;
    border-radius: 8px;
    background: var(--accent);
    color: white;
    border: 0;
    cursor: pointer
}

.physics-lesson .muted {
    color: var(--muted)
}

.physics-lesson .quote {
    padding: 12px;
    border-left: 4px solid var(--accent);
    background: linear-gradient(90deg, rgba(0,102,204,0.04), transparent);
    border-radius: 8px
}

.physics-lesson table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 8px
}

.physics-lesson td,
.physics-lesson th {
    padding: 8px;
    border-bottom: 1px solid #eef2f7;
    text-align: left
}

.physics-lesson .quiz-list {
    display: flex;
    flex-direction: column;
    gap: 14px
}

.physics-lesson .q {
    padding: 12px;
    border-radius: 10px;
    border: 1px solid #eef2f7
}

.physics-lesson .choices {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-top: 10px
}

.physics-lesson label.choice {
    display: flex;
    gap: 8px;
    align-items: flex-start;
    cursor: pointer
}

.physics-lesson input[type='radio'],
.physics-lesson input[type='checkbox'] {
    margin-top: 4px
}

.physics-lesson .result {
    margin-top: 12px;
    padding: 10px;
    border-radius: 8px
}

.physics-lesson .success {
    background: #ecfdf5;
    color: #065f46;
    border: 1px solid #bbf7d0
}

.physics-lesson .danger {
    background: #fff1f2;
    color: #9f1239;
    border: 1px solid #fecaca
}

.physics-lesson footer {
    margin-top: 18px;
    text-align: center;
    color: var(--muted);
    font-size: 13px
}

.physics-lesson .controls {
    display: flex;
    gap: 8px;
    flex-wrap: wrap
}

.physics-lesson .print {
    background: transparent;
    border: 1px solid #dbeafe;
    color: var(--accent);
    padding: 8px 10px;
    border-radius: 8px;
    cursor: pointer
}

.physics-lesson .small-btn {
    padding: 6px 8px;
    border-radius: 6px;
    border: 1px solid #e6eefc;
    background: white;
    cursor: pointer
}