.yt-share-app {
    --yt-primary: #06b6d4;
    --yt-primary-strong: #0891b2;
    --yt-primary-soft: rgba(6, 182, 212, 0.12);
    --yt-primary-fade: rgba(6, 182, 212, 0.07);
    --yt-bg: var(--bg-body, #f5f7fa);
    --yt-surface: var(--bg-section, #ffffff);
    --yt-surface-alt: #f8fbfd;
    --yt-surface-deep: #eef6fb;
    --yt-border: rgba(44, 62, 80, 0.12);
    --yt-text: var(--text-primary, #2c3e50);
    --yt-muted: var(--text-secondary, #627384);
    --yt-hero-glow: rgba(255, 255, 255, 0.24);
    --yt-step-bg: rgba(255, 255, 255, 0.72);
    --yt-step-border: rgba(6, 182, 212, 0.12);
    --yt-panel-tint: linear-gradient(180deg, rgba(6, 182, 212, 0.025), rgba(255, 255, 255, 0) 18%);
    --yt-input-bg: linear-gradient(180deg, var(--yt-surface-alt), #fdfefe);
    --yt-input-bg-focus: var(--yt-surface);
    --yt-input-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85);
    --yt-player-shell-bg: linear-gradient(180deg, #f8fbfd, #f2f7fb);
    --yt-player-shell-border: #dde8ef;
    --yt-player-shell-inset: inset 0 1px 0 rgba(255, 255, 255, 0.95);
    --yt-player-frame-bg: linear-gradient(180deg, #e7eef4, #dde7ee);
    --yt-empty-bg: linear-gradient(180deg, #edf3f7, #e2ebf2);
    --yt-empty-icon-bg: #ffffff;
    --yt-secondary-button-bg: linear-gradient(180deg, #f4fbfe, #e8f6fb);
    --yt-secondary-button-hover-bg: linear-gradient(180deg, #eefaff, #dff4fb);
    --yt-secondary-button-color: var(--yt-primary-strong);
    --yt-secondary-button-border: #bfeaf4;
    --yt-ghost-button-bg: rgba(255, 255, 255, 0.8);
    --yt-ghost-button-hover-bg: var(--yt-surface-alt);
    --yt-shadow: 0 18px 42px rgba(44, 62, 80, 0.08);
    --yt-shadow-soft: 0 10px 24px rgba(44, 62, 80, 0.06);
    width: 100%;
    max-width: 72rem;
    display: grid;
    gap: var(--spacing-md);
    color: var(--yt-text);
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    position: relative;
}

body.dark-mode .yt-share-app {
    --yt-primary: #22d3ee;
    --yt-primary-strong: #06b6d4;
    --yt-primary-soft: rgba(34, 211, 238, 0.1);
    --yt-primary-fade: rgba(34, 211, 238, 0.14);
    --yt-bg: var(--bg-body, #1a1a1a);
    --yt-surface: var(--bg-section, #2d2d2d);
    --yt-surface-alt: #31363b;
    --yt-surface-deep: #272c31;
    --yt-border: rgba(255, 255, 255, 0.08);
    --yt-text: var(--text-primary, #ffffff);
    --yt-muted: var(--text-secondary, #cccccc);
    --yt-hero-glow: rgba(34, 211, 238, 0.09);
    --yt-step-bg: rgba(255, 255, 255, 0.025);
    --yt-step-border: rgba(34, 211, 238, 0.14);
    --yt-panel-tint: linear-gradient(180deg, rgba(34, 211, 238, 0.06), rgba(255, 255, 255, 0) 20%);
    --yt-input-bg: linear-gradient(180deg, #343a40, #2b3036);
    --yt-input-bg-focus: #363c43;
    --yt-input-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.05);
    --yt-player-shell-bg: linear-gradient(180deg, #343a41, #2e343b);
    --yt-player-shell-border: rgba(255, 255, 255, 0.08);
    --yt-player-shell-inset: inset 0 1px 0 rgba(255, 255, 255, 0.05);
    --yt-player-frame-bg: #23282e;
    --yt-empty-bg: linear-gradient(180deg, rgba(255, 255, 255, 0.03), rgba(255, 255, 255, 0.015)), #262c32;
    --yt-empty-icon-bg: #30363d;
    --yt-secondary-button-bg: linear-gradient(180deg, rgba(34, 211, 238, 0.1), rgba(34, 211, 238, 0.06));
    --yt-secondary-button-hover-bg: linear-gradient(180deg, rgba(34, 211, 238, 0.16), rgba(34, 211, 238, 0.1));
    --yt-secondary-button-color: #baf4ff;
    --yt-secondary-button-border: rgba(34, 211, 238, 0.22);
    --yt-ghost-button-bg: linear-gradient(180deg, #3a4046, #33383e);
    --yt-ghost-button-hover-bg: linear-gradient(180deg, #444b52, #3b4148);
    --yt-shadow: 0 18px 36px rgba(0, 0, 0, 0.22);
    --yt-shadow-soft: 0 10px 24px rgba(0, 0, 0, 0.15);
}

.yt-card {
    position: relative;
    overflow: hidden;
    background: var(--yt-surface);
    border: 1px solid var(--yt-border);
    border-radius: 1.35rem;
    box-shadow: var(--yt-shadow);
}

.yt-hero {
    display: grid;
    align-items: center;
    min-height: 11rem;
    padding: 1.75rem 1.8rem;
    background:
        linear-gradient(135deg, rgba(6, 182, 212, 0.035), rgba(255, 255, 255, 0) 48%),
        var(--yt-surface);
}

.yt-hero::before {
    display: none;
}

.yt-hero-copy {
    max-width: 100%;
    position: relative;
    z-index: 1;
}

.yt-hero h2,
.yt-controls h2 {
    margin: 0;
    text-align: left;
    font-size: clamp(1.45rem, 2.8vw, 2.35rem);
    line-height: 1.15;
    letter-spacing: -0.02em;
    color: var(--yt-text);
}

.yt-steps {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 0.9rem;
    margin-top: 1rem;
}

.yt-step-card {
    display: flex;
    align-items: flex-start;
    gap: 0.8rem;
    padding: 1rem;
    border: 1px solid var(--yt-step-border);
    border-radius: 1rem;
    background: var(--yt-step-bg);
    box-shadow: var(--yt-shadow-soft);
}

.yt-step-number {
    width: 2rem;
    height: 2rem;
    flex: 0 0 2rem;
    display: grid;
    place-items: center;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--yt-primary), var(--yt-primary-strong));
    color: #ffffff;
    font-size: 0.92rem;
    font-weight: 700;
    box-shadow: 0 8px 16px rgba(6, 182, 212, 0.24);
}

.yt-step-copy h3 {
    margin: 0;
    font-size: 0.98rem;
    color: var(--yt-text);
}

.yt-step-copy p {
    margin: 0.28rem 0 0;
    color: var(--yt-muted);
    font-size: 0.88rem;
    line-height: 1.5;
}

.yt-layout {
    display: grid;
    grid-template-columns: minmax(19rem, 24rem) minmax(0, 1fr);
    gap: var(--spacing-md);
    align-items: stretch;
}

.yt-controls,
.yt-stage {
    padding: 1.35rem;
    height: 100%;
}

.yt-controls {
    display: grid;
    gap: 0.85rem;
    align-content: start;
    background: var(--yt-panel-tint), var(--yt-surface);
}

.yt-section-heading {
    margin-bottom: 0.5rem;
    padding-bottom: 0.7rem;
    border-bottom: 1px solid var(--yt-border);
}

.yt-label {
    color: var(--yt-muted);
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.yt-input,
.yt-textarea {
    width: 100%;
    color: var(--yt-text);
    font: inherit;
    background: var(--yt-input-bg);
    border: 1px solid var(--yt-border);
    border-radius: 1rem;
    box-shadow: var(--yt-input-shadow);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast), background-color var(--transition-fast), transform var(--transition-fast);
}

.yt-input {
    min-height: 3rem;
    padding: 0.9rem 1rem;
}

.yt-textarea {
    min-height: 8rem;
    resize: vertical;
    padding: 0.9rem 1rem;
    line-height: 1.6;
}

.yt-input::placeholder,
.yt-textarea::placeholder {
    color: var(--yt-muted);
    opacity: 0.7;
}

.yt-input:hover,
.yt-textarea:hover {
    border-color: color-mix(in srgb, var(--yt-primary) 20%, var(--yt-border));
}

.yt-input:focus,
.yt-textarea:focus {
    outline: none;
    border-color: var(--yt-primary);
    box-shadow: 0 0 0 4px var(--yt-primary-soft);
    background: var(--yt-input-bg-focus);
    transform: translateY(-1px);
}

.yt-input-readonly {
    color: var(--yt-muted);
    font-size: 0.92rem;
}

.yt-actions {
    display: flex;
    flex-direction: column;
    gap: 0.7rem;
    margin-top: 0.35rem;
}

.yt-button {
    min-height: 3rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.55rem;
    border-radius: 1rem;
    border: 1px solid transparent;
    font: inherit;
    font-weight: 600;
    letter-spacing: 0.01em;
    cursor: pointer;
    transition: transform var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast), box-shadow var(--transition-fast);
}

.yt-button:hover {
    transform: translateY(-2px);
}

.yt-button:active {
    transform: translateY(0);
}

.yt-button-primary {
    background: linear-gradient(135deg, var(--yt-primary), var(--yt-primary-strong));
    color: #ffffff;
    box-shadow: 0 12px 28px rgba(6, 182, 212, 0.24);
}

.yt-button-primary:hover {
    box-shadow: 0 16px 32px rgba(6, 182, 212, 0.28);
}

.yt-button-secondary {
    background: var(--yt-secondary-button-bg);
    color: var(--yt-secondary-button-color);
    border-color: var(--yt-secondary-button-border);
    box-shadow: var(--yt-shadow-soft);
}

.yt-button-secondary:hover {
    background: var(--yt-secondary-button-hover-bg);
}

.yt-button-ghost {
    background: var(--yt-ghost-button-bg);
    color: var(--yt-muted);
    border-color: var(--yt-border);
}

.yt-button-ghost:hover {
    color: var(--yt-text);
    background: var(--yt-ghost-button-hover-bg);
}

.yt-status {
    margin: 0.15rem 0 0;
    min-height: 1.5rem;
    color: var(--yt-muted);
    font-size: 0.88rem;
    font-weight: 600;
}

.yt-status.is-success {
    color: var(--yt-primary-strong);
}

.yt-status.is-error {
    color: #d9534f;
}

.yt-footnote {
    color: var(--yt-muted);
    font-size: 0.84rem;
}

.yt-stage {
    display: grid;
    gap: 1rem;
    align-content: stretch;
    padding: 1.2rem;
    background: var(--yt-panel-tint), var(--yt-surface);
    border: 1px solid var(--yt-border);
    box-shadow: var(--yt-shadow);
}

.yt-player-shell {
    display: grid;
    height: 100%;
    align-content: center;
    padding: 0;
    border-radius: 0;
    background: transparent;
    border: none;
    box-shadow: none;
}

.yt-player-frame {
    position: relative;
    width: 100%;
    aspect-ratio: 16 / 9;
    overflow: hidden;
    border-radius: 1.05rem;
    background: var(--yt-player-frame-bg);
    box-shadow: none;
}

.yt-player-frame iframe,
.yt-player-frame .yt-empty-state {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

.yt-empty-state {
    display: grid;
    place-items: center;
    padding: 1.5rem;
    text-align: center;
    color: var(--yt-text);
    background: var(--yt-empty-bg);
}

.yt-empty-icon {
    width: 6.2rem;
    height: 6.2rem;
    display: grid;
    place-items: center;
    margin: 0 auto;
    border-radius: 1.5rem;
    background: var(--yt-empty-icon-bg);
    color: var(--yt-primary);
    box-shadow: 0 10px 22px rgba(44, 62, 80, 0.12);
    font-size: 2.9rem;
}

.yt-empty-state[hidden] {
    display: none;
}

body.youtube-student-view .yt-hero,
body.youtube-student-view .yt-controls {
    display: none;
}

body.youtube-student-view .yt-layout {
    grid-template-columns: 1fr;
}

body.youtube-student-view .yt-share-app {
    gap: 0;
}

@media screen and (max-width: 68rem) {
    .yt-layout {
        grid-template-columns: 1fr;
    }
}

@media screen and (max-width: 48rem) {
    .yt-share-app {
        gap: var(--spacing-sm);
    }

    .yt-hero,
    .yt-controls,
    .yt-stage {
        padding: 1rem;
    }

    .yt-actions {
        display: grid;
    }

    .yt-steps {
        grid-template-columns: 1fr;
    }

    .yt-empty-icon {
        width: 5.2rem;
        height: 5.2rem;
        font-size: 2.35rem;
    }

    .yt-player-shell {
        padding: 0;
        border-radius: 0;
    }

    .yt-player-frame {
        border-radius: 0.95rem;
        overflow: hidden;
        box-shadow: none;
    }
}