/* Fixed Intro Box */
.fixed-intro-box {
    position: absolute;
    top: 50%;
    left: 60%;
    transform: translate(-50%, -50%) translateY(30px);
    max-width: 700px;
    width: 90%;
    padding: 40px 50px;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(15px);
    -webkit-backdrop-filter: blur(15px);
    border-radius: 4px;
    border: 1px solid var(--hud-border);
    z-index: 5;
    opacity: 0;
    transition: opacity 0.8s ease-out 0.3s,
        transform 0.8s ease-out 0.3s;
}

.fixed-intro-box.visible {
    opacity: 1;
    transform: translate(-50%, -50%) translateY(0);
}

.fixed-intro-box p {
    font-size: 1.1em;
    line-height: 1.8;
    margin-bottom: 20px;
    color: rgba(255, 255, 255, 0.9);
}

.fixed-intro-box strong {
    color: var(--accent-rust);
    letter-spacing: 1px;
}

.fixed-intro-box .universe-highlight {
    color: #d45a2a;
    letter-spacing: 1.5px;
}

/* Book Title Buttons */
.book-titles {
    margin-top: 40px;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.book-title-btn {
    background: transparent;
    border: 1px solid var(--accent-rust-glow);
    color: #fff;
    font-family: var(--font-mono);
    font-size: 0.95em;
    letter-spacing: 3px;
    padding: 15px 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: left;
    position: relative;
    overflow: hidden;
}

.book-title-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: var(--accent-rust-glow);
    transition: left 0.3s ease;
    z-index: -1;
}

.book-title-btn:hover::before {
    left: 0;
}

.book-title-btn:hover {
    border-color: var(--accent-rust);
    box-shadow: 0 0 20px var(--accent-rust-glow);
}

.book-title-btn .bracket {
    color: var(--accent-rust);
    opacity: 0.7;
}

/* Panel Overlay */
.panel-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
    z-index: 9998;
}

.panel-overlay.active {
    opacity: 1;
    visibility: visible;
}

/* Slide-out Panels */
.book-panel {
    position: fixed;
    top: 0;
    right: 0;
    width: 600px;
    max-width: 90vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-left: 1px solid var(--accent-rust-glow);
    transform: translateX(100%);
    transition: transform 0.4s cubic-bezier(0.4, 0.0, 0.2, 1);
    z-index: 9999;
    overflow-y: auto;
    padding: 60px 40px 40px 40px;
}

.book-panel.active {
    transform: translateX(0);
}

/* Panel Close Button */
.panel-close {
    position: absolute;
    top: 20px;
    right: 20px;
    background: transparent;
    border: none;
    color: var(--accent-rust);
    font-size: 2.5em;
    cursor: pointer;
    line-height: 1;
    padding: 0;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    z-index: 10;
}

.panel-close:hover {
    color: #fff;
    transform: rotate(90deg);
}

/* Panel Content */
.panel-content {
    color: #fff;
}

.panel-content .hud-technical-label {
    display: block;
    margin-bottom: 20px;
}

.panel-content h3 {
    font-family: var(--font-mono);
    font-size: 1.8em;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 2px;
    margin-bottom: 10px;
    color: var(--accent-rust);
}

.panel-content .tagline {
    font-family: var(--font-mono);
    font-size: 1em;
    letter-spacing: 1px;
    color: var(--text-muted);
    margin-bottom: 30px;
    text-transform: uppercase;
}

.panel-content p {
    font-size: 0.88em;
    line-height: 1.7;
    margin-bottom: 18px;
    color: rgba(255, 255, 255, 0.85);
}

.panel-content .summary {
    border-left: 3px solid var(--accent-rust);
    padding-left: 20px;
    font-weight: 600;
    margin-top: 30px;
    font-style: italic;
}

/* Responsive */
@media (max-width: 768px) {
    .fixed-intro-box {
        position: relative;
        top: 0;
        left: 0;
        transform: none !important;
        width: 100%;
        max-width: 100%;
        margin-top: 40px;
        margin-bottom: 40px;
        padding: 30px 20px;
        border: none;
        border-top: 1px solid var(--hud-border);
        border-bottom: 1px solid var(--hud-border);
        background: rgba(0, 0, 0, 0.7);
    }

    .fixed-intro-box p {
        font-size: 1em;
    }

    .book-titles {
        margin-top: 25px;
    }

    .book-title-btn {
        font-size: 0.85em;
        padding: 12px 15px;
    }

    .book-panel {
        width: 100%;
        max-width: 100%;
        padding: 50px 25px 25px 25px;
    }

    .panel-content h3 {
        font-size: 1.4em;
    }
}

/* Prevent body scroll when panel is open */
body.panel-open {
    overflow: hidden;
}