:root {
    --lesson-bg: #0b1220;
    --lesson-surface: #111c2f;
    --lesson-surface-strong: #16243b;
    --lesson-border: rgba(148, 163, 184, 0.18);
    --lesson-text: #eef4ff;
    --lesson-muted: #9eacc1;
    --lesson-accent: #62d8ff;
    --lesson-accent-strong: #8d7aff;
    --lesson-success: #7be3b0;
    --lesson-danger: #ff9eaa;
    color-scheme: dark;
}

* {
    box-sizing: border-box;
}

body {
    min-height: 100vh;
    margin: 0;
    color: var(--lesson-text);
    background:
        radial-gradient(circle at 12% 0%, rgba(98, 216, 255, 0.13), transparent 34rem),
        radial-gradient(circle at 90% 20%, rgba(141, 122, 255, 0.12), transparent 30rem),
        var(--lesson-bg);
    font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

button,
input {
    font: inherit;
}

button,
a {
    -webkit-tap-highlight-color: transparent;
}

a {
    color: inherit;
}

[hidden] {
    display: none !important;
}

.lesson-topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    width: min(1180px, calc(100% - 2rem));
    margin: 0 auto;
    padding: 1.2rem 0;
    border-bottom: 1px solid var(--lesson-border);
}

.lesson-brand {
    display: inline-flex;
    align-items: center;
    gap: 0.75rem;
    text-decoration: none;
}

.lesson-brand-mark {
    display: grid;
    width: 2.65rem;
    height: 2.65rem;
    place-items: center;
    border: 1px solid rgba(98, 216, 255, 0.5);
    border-radius: 0.8rem;
    color: #07121f;
    background: linear-gradient(135deg, var(--lesson-accent), #b5f0ff);
    font-weight: 900;
    letter-spacing: -0.08em;
}

.lesson-brand strong,
.lesson-brand small {
    display: block;
}

.lesson-brand strong {
    font-size: 0.95rem;
}

.lesson-brand small {
    margin-top: 0.15rem;
    color: var(--lesson-muted);
    font-size: 0.74rem;
}

.lesson-top-actions {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: 0.7rem;
    color: var(--lesson-muted);
    font-size: 0.82rem;
}

.lesson-top-actions a {
    text-decoration: none;
}

.lesson-top-actions a:hover,
.lesson-footer a:hover {
    color: var(--lesson-accent);
}

.lesson-user-label {
    max-width: 14rem;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    color: var(--lesson-text);
}

.lesson-shell {
    width: min(1180px, calc(100% - 2rem));
    min-height: calc(100vh - 11rem);
    margin: 0 auto;
    padding: 4rem 0 5rem;
}

.auth-layout {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(20rem, 27rem);
    align-items: center;
    gap: clamp(2rem, 8vw, 7rem);
    min-height: 54vh;
}

.auth-intro {
    max-width: 37rem;
}

.eyebrow {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--lesson-accent);
    font-size: 0.72rem;
    font-weight: 800;
    letter-spacing: 0.14em;
}

.auth-intro h1,
.library-heading h1,
.viewer-heading h1 {
    margin: 0.7rem 0 1rem;
    color: #fff;
    font-size: clamp(2.1rem, 5vw, 4.8rem);
    line-height: 1.03;
    letter-spacing: -0.06em;
}

.auth-intro p,
.library-heading p,
.viewer-heading p {
    max-width: 38rem;
    margin: 0;
    color: var(--lesson-muted);
    font-size: 1.04rem;
    line-height: 1.75;
}

.security-points {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    margin-top: 2rem;
}

.security-points span,
.viewer-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.6rem 0.8rem;
    border: 1px solid var(--lesson-border);
    border-radius: 999px;
    color: #c8d7eb;
    background: rgba(255, 255, 255, 0.035);
    font-size: 0.78rem;
}

.auth-card {
    padding: clamp(1.5rem, 4vw, 2.3rem);
    border: 1px solid rgba(98, 216, 255, 0.23);
    border-radius: 1.35rem;
    background: linear-gradient(145deg, rgba(22, 36, 59, 0.96), rgba(13, 23, 40, 0.96));
    box-shadow: 0 2rem 5rem rgba(0, 0, 0, 0.25);
}

.auth-card h2 {
    margin: 0.7rem 0 0.5rem;
    font-size: 1.7rem;
}

.auth-card > p {
    margin: 0 0 1.4rem;
    color: var(--lesson-muted);
    font-size: 0.9rem;
    line-height: 1.55;
}

.lesson-form {
    display: grid;
    gap: 0.55rem;
}

.lesson-form label {
    margin-top: 0.45rem;
    color: #cad6e7;
    font-size: 0.82rem;
    font-weight: 700;
}

.lesson-form input {
    width: 100%;
    padding: 0.82rem 0.9rem;
    border: 1px solid var(--lesson-border);
    border-radius: 0.65rem;
    outline: none;
    color: var(--lesson-text);
    background: rgba(3, 9, 19, 0.4);
}

.lesson-form input:focus {
    border-color: var(--lesson-accent);
    box-shadow: 0 0 0 3px rgba(98, 216, 255, 0.13);
}

.lesson-password-field {
    position: relative;
}

.lesson-password-field input {
    padding-right: 3.5rem;
}

.lesson-password-field .password-toggle {
    position: absolute;
    top: 50%;
    right: 0.35rem;
    display: grid;
    width: 2.65rem;
    height: 2.65rem;
    place-items: center;
    padding: 0;
    transform: translateY(-50%);
    border: 0;
    border-radius: 0.5rem;
    color: var(--lesson-muted);
    background: transparent;
    cursor: pointer;
}

.lesson-password-field .password-toggle:hover,
.lesson-password-field .password-toggle:focus-visible {
    color: var(--lesson-text);
    background: rgba(255, 255, 255, 0.08);
}

.lesson-password-field .password-toggle:focus-visible {
    outline: 2px solid var(--lesson-accent);
    outline-offset: 2px;
}

.lesson-password-field .password-toggle svg {
    width: 1.3rem;
    height: 1.3rem;
}

.lesson-password-field .password-toggle .eye-slash {
    display: none;
}

.lesson-password-field .password-toggle[aria-pressed="true"] .eye-slash {
    display: block;
}

.button,
.icon-button {
    border: 1px solid transparent;
    border-radius: 0.65rem;
    cursor: pointer;
    transition: transform 0.2s ease, border-color 0.2s ease, background 0.2s ease, opacity 0.2s ease;
}

.button {
    padding: 0.7rem 0.95rem;
    color: var(--lesson-text);
    background: rgba(255, 255, 255, 0.06);
    font-size: 0.82rem;
    font-weight: 750;
}

.button:hover:not(:disabled),
.icon-button:hover:not(:disabled) {
    transform: translateY(-1px);
}

.button:disabled,
.icon-button:disabled {
    cursor: not-allowed;
    opacity: 0.4;
}

.button-primary {
    margin-top: 0.8rem;
    color: #07121f;
    background: linear-gradient(135deg, var(--lesson-accent), #c0f3ff);
}

.button-primary:hover:not(:disabled) {
    box-shadow: 0 0.6rem 1.5rem rgba(98, 216, 255, 0.2);
}

.button-google {
    display: flex;
    width: 100%;
    align-items: center;
    justify-content: center;
    gap: 0.6rem;
    border-color: rgba(255, 255, 255, 0.2);
    background: rgba(255, 255, 255, 0.08);
}

.button-google:hover:not(:disabled) {
    border-color: rgba(255, 255, 255, 0.42);
    background: rgba(255, 255, 255, 0.13);
}

.google-mark {
    display: grid;
    width: 1.35rem;
    height: 1.35rem;
    place-items: center;
    border-radius: 50%;
    color: #4285f4;
    background: #fff;
    font-family: Arial, sans-serif;
    font-size: 0.9rem;
    font-weight: 800;
}

.auth-divider {
    display: flex;
    align-items: center;
    gap: 0.7rem;
    margin: 1.2rem 0 0.85rem;
    color: #7f91aa;
    font-size: 0.72rem;
    text-transform: uppercase;
}

.auth-divider::before,
.auth-divider::after {
    flex: 1;
    height: 1px;
    content: "";
    background: var(--lesson-border);
}

.button-quiet {
    border-color: var(--lesson-border);
}

.auth-toggle {
    width: 100%;
    margin-top: 0.9rem;
    padding: 0.3rem;
    border: 0;
    color: var(--lesson-accent);
    background: transparent;
    cursor: pointer;
    font-size: 0.82rem;
}

.auth-note {
    margin-top: 1.35rem !important;
    color: #7f91aa !important;
    font-size: 0.74rem !important;
}

.inline-message {
    min-height: 1.4rem;
    margin: 0.8rem 0 0;
    color: var(--lesson-muted);
    font-size: 0.88rem;
    line-height: 1.5;
}

.inline-message.success {
    color: var(--lesson-success);
}

.inline-message.error {
    color: var(--lesson-danger);
}

.library-heading,
.viewer-heading-main {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 1.5rem;
}

.library-heading {
    margin-bottom: 1.6rem;
}

.library-heading h1 {
    margin-bottom: 0.55rem;
    font-size: clamp(2.1rem, 5vw, 3.8rem);
}

.discipline-list {
    display: grid;
    gap: 1.25rem;
    margin-top: 0.6rem;
}

.discipline-section {
    padding: 1.25rem;
    border: 1px solid var(--lesson-border);
    border-radius: 1.25rem;
    background: rgba(12, 23, 40, 0.78);
}

.discipline-heading {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 1rem;
}

.discipline-heading h2 {
    margin: 0.55rem 0 0.45rem;
    color: #fff;
    font-size: clamp(1.3rem, 2.5vw, 1.85rem);
}

.discipline-heading p {
    max-width: 50rem;
    margin: 0;
    color: var(--lesson-muted);
    font-size: 0.88rem;
    line-height: 1.55;
}

.discipline-count {
    flex: 0 0 auto;
    padding: 0.4rem 0.65rem;
    border: 1px solid rgba(98, 216, 255, 0.22);
    border-radius: 999px;
    color: var(--lesson-accent);
    font-size: 0.72rem;
    font-weight: 800;
    white-space: nowrap;
}

.discipline-topics {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
    margin-top: 1rem;
}

.discipline-topic {
    padding: 0.38rem 0.6rem;
    border: 1px solid rgba(148, 163, 184, 0.16);
    border-radius: 0.55rem;
    color: #b7c5d7;
    background: rgba(17, 28, 47, 0.62);
    font-size: 0.73rem;
}

.discipline-content {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 1rem;
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid rgba(148, 163, 184, 0.1);
}

.discipline-empty {
    grid-column: 1 / -1;
    padding: 1.15rem;
    border: 1px dashed rgba(148, 163, 184, 0.24);
    border-radius: 0.9rem;
    color: var(--lesson-muted);
    background: rgba(17, 28, 47, 0.48);
}

.discipline-empty strong {
    display: block;
    margin-bottom: 0.35rem;
    color: #d8e5f2;
    font-size: 0.9rem;
}

.discipline-empty p {
    margin: 0;
    font-size: 0.82rem;
}

.lesson-card {
    display: flex;
    min-height: 16rem;
    flex-direction: column;
    padding: 1.35rem;
    border: 1px solid var(--lesson-border);
    border-radius: 1rem;
    background: rgba(17, 28, 47, 0.8);
    transition: transform 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.lesson-card:hover {
    transform: translateY(-3px);
    border-color: rgba(98, 216, 255, 0.6);
    background: var(--lesson-surface-strong);
}

.lesson-card-category {
    color: var(--lesson-accent);
    font-size: 0.7rem;
    font-weight: 800;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.lesson-card h2 {
    margin: 0.75rem 0 0.55rem;
    font-size: 1.2rem;
}

.lesson-card p {
    flex: 1;
    margin: 0;
    color: var(--lesson-muted);
    font-size: 0.87rem;
    line-height: 1.55;
}

.lesson-card-footer {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: 0.8rem;
    margin-top: 1.4rem;
}

.lesson-card .button {
    color: #07121f;
    background: var(--lesson-accent);
}

.viewer-view {
    max-width: 1100px;
    margin: 0 auto;
}

.back-link {
    padding: 0;
    border: 0;
    color: var(--lesson-accent);
    background: transparent;
    cursor: pointer;
    font-size: 0.86rem;
}

.viewer-heading {
    margin-bottom: 1.3rem;
}

.viewer-heading-main {
    align-items: flex-start;
    margin-top: 1.35rem;
}

.viewer-heading h1 {
    margin-bottom: 0.6rem;
    font-size: clamp(1.8rem, 4vw, 3.2rem);
}

.viewer-heading p {
    font-size: 0.9rem;
}

.viewer-badge {
    flex: 0 0 auto;
    color: var(--lesson-success);
    border-color: rgba(123, 227, 176, 0.28);
}

.viewer-toolbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    margin: 1rem 0;
    padding: 0.65rem;
    border: 1px solid var(--lesson-border);
    border-radius: 0.8rem;
    background: rgba(17, 28, 47, 0.85);
}

.viewer-page-controls,
.viewer-zoom-controls {
    display: flex;
    align-items: center;
    gap: 0.6rem;
}

.viewer-page-controls span,
.viewer-zoom-controls span {
    min-width: 6.7rem;
    color: #c7d4e6;
    font-size: 0.78rem;
    text-align: center;
}

.icon-button {
    display: grid;
    width: 2.2rem;
    height: 2.2rem;
    place-items: center;
    border-color: var(--lesson-border);
    color: var(--lesson-text);
    background: rgba(255, 255, 255, 0.06);
    font-size: 1.3rem;
}

.viewer-frame {
    min-height: 32rem;
    overflow: hidden;
    border: 1px solid var(--lesson-border);
    border-radius: 0.9rem;
    background: #263145;
    box-shadow: 0 1.5rem 3rem rgba(0, 0, 0, 0.22);
}

.viewer-canvas-wrap {
    position: relative;
    display: flex;
    min-height: 32rem;
    align-items: flex-start;
    justify-content: center;
    overflow: auto;
    padding: 1.2rem;
}

#lesson-pdf-canvas {
    display: block;
    max-width: none;
    min-height: 14rem;
    background: #fff;
    box-shadow: 0 0.8rem 2.2rem rgba(0, 0, 0, 0.26);
}

.viewer-watermark {
    position: absolute;
    z-index: 2;
    top: 50%;
    left: 50%;
    width: max-content;
    max-width: 80%;
    transform: translate(-50%, -50%) rotate(-24deg);
    color: rgba(15, 38, 66, 0.1);
    font-size: clamp(1.1rem, 4vw, 2.2rem);
    font-weight: 900;
    letter-spacing: 0.08em;
    pointer-events: none;
    text-transform: uppercase;
}

.viewer-empty {
    position: absolute;
    inset: 0;
    display: grid;
    min-height: 32rem;
    place-content: center;
    justify-items: center;
    color: var(--lesson-muted);
    background: rgba(38, 49, 69, 0.8);
}

.viewer-empty p {
    margin: 0.8rem 0 0;
    font-size: 0.85rem;
}

.loading-spinner {
    width: 2rem;
    height: 2rem;
    border: 3px solid rgba(255, 255, 255, 0.18);
    border-top-color: var(--lesson-accent);
    border-radius: 50%;
    animation: lesson-spin 0.8s linear infinite;
}

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

.viewer-footnote {
    margin: 0.9rem 0 0;
    color: #7f91aa;
    font-size: 0.74rem;
    line-height: 1.5;
    text-align: center;
}

.lesson-footer {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    width: min(1180px, calc(100% - 2rem));
    margin: 0 auto;
    padding: 1.3rem 0 2rem;
    border-top: 1px solid var(--lesson-border);
    color: #7f91aa;
    font-size: 0.76rem;
}

.lesson-footer a {
    text-decoration: none;
}

@media (max-width: 860px) {
    .auth-layout {
        grid-template-columns: 1fr;
        gap: 2rem;
        max-width: 38rem;
        margin: 0 auto;
    }

    .discipline-content {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (max-width: 620px) {
    .lesson-topbar,
    .lesson-top-actions,
    .library-heading,
    .discipline-heading,
    .viewer-heading-main,
    .viewer-toolbar,
    .lesson-footer {
        align-items: flex-start;
        flex-direction: column;
    }

    .lesson-topbar {
        padding: 0.9rem 0;
    }

    .lesson-top-actions {
        width: 100%;
        flex-direction: row;
        flex-wrap: wrap;
    }

    .lesson-shell {
        padding-top: 2.8rem;
    }

    .auth-intro h1,
    .library-heading h1 {
        font-size: 2.45rem;
    }

    .discipline-content {
        grid-template-columns: 1fr;
    }

    .viewer-toolbar {
        gap: 0.8rem;
    }

    .viewer-page-controls {
        width: 100%;
        justify-content: space-between;
    }

    .viewer-zoom-controls {
        align-self: flex-end;
    }

    .viewer-frame,
    .viewer-canvas-wrap,
    .viewer-empty {
        min-height: 24rem;
    }

    .lesson-footer {
        gap: 0.5rem;
    }
}