/* ==========================================================================
   Paula's Birthday Card - High-Fidelity 3D Book Layout
   ========================================================================== */

/* Design Tokens & System Variables */
:root {
    /* Color Palette */
    --color-bg-main: #FDFBF7;        /* Soft warm luxury cream */
    --color-card-bg: #FFFFFF;        /* Pure white */
    --color-primary: #722F37;        /* Deep wine burgundy */
    --color-primary-light: #A36B73;  /* Dusty rose */
    --color-accent: #C5A059;         /* Matte gold */
    --color-accent-hover: #D9B873;   /* Shimmering gold */
    --color-text-dark: #2A2022;      /* Off-black with warm plum undertones */
    --color-text-light: #6E5E60;     /* Soft warm gray for description body */
    --color-success: #4C7A5C;        /* Sage green for advantages */
    --color-warning: #C28C5F;        /* Soft amber/terracotta for disadvantages */
    
    /* Spacing System */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2.2rem;
    --spacing-xl: 3.5rem;

    /* Typographic System */
    --font-serif: 'Cormorant Garamond', Georgia, serif;
    --font-display: 'Playfair Display', Times, serif;
    --font-sans: 'Outfit', system-ui, sans-serif;

    /* Borders & Shadow System */
    --border-radius-lg: 20px;
    --border-radius-md: 12px;
    --border-radius-sm: 8px;
    --shadow-soft: 0 8px 30px rgba(114, 47, 55, 0.04);
    --shadow-medium: 0 16px 40px rgba(42, 32, 34, 0.08);
    --shadow-peel: -15px 15px 25px rgba(0, 0, 0, 0.15);
    
    /* Animation Timings */
    --transition-peel: 1.2s cubic-bezier(0.25, 1, 0.5, 1);
    --transition-hover: 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Base Reset & Styling */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: var(--color-bg-main);
    color: var(--color-text-dark);
    font-family: var(--font-sans);
    overflow: hidden;
    width: 100vw;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    -webkit-font-smoothing: antialiased;
}

/* Background Particles */
#particle-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
    pointer-events: none;
    opacity: 0.85;
}

.ambient-glow {
    position: absolute;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(244, 218, 222, 0.4) 0%, rgba(253, 251, 247, 0) 70%);
    border-radius: 50%;
    z-index: 0;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    pointer-events: none;
}

.viewport {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 2;
    perspective: 2000px;
}

/* ==========================================================================
   3D Book Layout & Engine (Scale + State Translates)
   ========================================================================== */
.book {
    position: relative;
    width: 900px;
    height: 650px;
    flex-shrink: 0; /* Lock dimensions to prevent flexbox collapsing */
    min-width: 900px;
    transform: scale(var(--book-scale, 1)) translateX(var(--book-translate-x, -25%));
    transform-origin: center center;
    transition: transform var(--transition-peel);
    transform-style: preserve-3d;
}

/* Page states translates */
.book.state-1 {
    --book-translate-x: -25%;
}
.book.state-2 {
    --book-translate-x: 0%;
}
.book.state-3 {
    --book-translate-x: 0%;
}

/* Sheet classes: width 50% to align with spine center */
.sheet {
    position: absolute;
    width: 50%;
    height: 100%;
    top: 0;
    left: 50%;
    transform-style: preserve-3d;
    transform-origin: left center;
    transition: transform var(--transition-peel), opacity 0.5s ease, visibility 0s linear;
    opacity: 1;
    pointer-events: auto;
}

#sheet-1 {
    z-index: 10;
}
#sheet-2 {
    z-index: 8;
    pointer-events: none;
}
.book.open #sheet-2 {
    pointer-events: auto;
}

.sheet.flipped {
    transform: rotateY(-180deg);
}

/* ==========================================================================
   WebKit 3D Depth Layer Glitch Fixes (Visibility Rules)
   ========================================================================== */
.book.state-1 #sheet-1 {
    visibility: visible;
    transition-delay: 0s;
}
.book.state-1 #sheet-2 {
    visibility: hidden;
    transition-delay: 1.2s;
}
.book.state-2 #sheet-1 {
    visibility: visible;
    transition-delay: 0s;
}
.book.state-2 #sheet-2 {
    visibility: visible;
    transition-delay: 0s;
}

@media (max-width: 950px) {
    .book.state-2 #sheet-2 {
        visibility: hidden;
        transition-delay: 1.2s;
    }
}

.book.state-3 #sheet-1 {
    visibility: hidden;
    transition-delay: 1.2s;
}
.book.state-3 #sheet-2 {
    visibility: visible;
    transition-delay: 0s;
}

/* Visual spine crease */
.book::before {
    content: '';
    position: absolute;
    left: 50%;
    top: 0;
    width: 30px;
    height: 100%;
    background: linear-gradient(to right, rgba(0,0,0,0.12) 0%, rgba(0,0,0,0) 100%);
    z-index: 15;
    pointer-events: none;
    transform: translateX(-50%);
    opacity: 0;
    transition: opacity var(--transition-peel);
}
.book.open::before {
    opacity: 1;
}

/* Page Faces */
.page {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    background-color: var(--color-card-bg);
    border-radius: 0 var(--border-radius-lg) var(--border-radius-lg) 0;
    padding: var(--spacing-lg) var(--spacing-md);
    box-shadow: var(--shadow-medium);
    backface-visibility: hidden;
    overflow: hidden;
}

.page.front {
    transform: rotateY(0deg);
    z-index: 2;
}

.page.back {
    transform: rotateY(180deg);
    border-radius: var(--border-radius-lg) 0 0 var(--border-radius-lg);
    z-index: 1;
}

/* Page backing fills */
.cover-back {
    background: linear-gradient(135deg, #FAF6F0 0%, #E5C0C4 100%);
    border: 1px solid rgba(197, 160, 89, 0.15);
}

/* Spacing overlays for pages */
.sheet::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to right, rgba(0, 0, 0, 0.1) 0%, rgba(0, 0, 0, 0) 30%, rgba(255, 255, 255, 0.15) 75%, rgba(0, 0, 0, 0.08) 100%);
    z-index: 12;
    pointer-events: none;
    opacity: 0;
    transition: opacity var(--transition-peel);
    backface-visibility: hidden;
}
.sheet.flipped::after {
    background: linear-gradient(to left, rgba(0, 0, 0, 0.1) 0%, rgba(0, 0, 0, 0) 30%, rgba(255, 255, 255, 0.15) 75%, rgba(0, 0, 0, 0.08) 100%);
}

/* Hide desktop-redundant elements in split view */
@media (min-width: 951px) {
    #btn-letter-next {
        display: none;
    }
    .cottage-header-nav {
        display: none;
    }
}

/* ==========================================================================
   Page 1: Cover Page
   ========================================================================== */
#cover-page {
    background: linear-gradient(rgba(255, 255, 255, 0.05), rgba(255, 255, 255, 0.05)), url('../assets/cover-bg.png');
    background-size: cover;
    background-position: center;
    display: flex;
    justify-content: center;
    align-items: center;
    border: 1px solid rgba(197, 160, 89, 0.15);
    padding: 4.8rem;
}

.cover-card {
    background: rgba(255, 255, 255, 0.82);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    width: 100%;
    height: 100%;
    border-radius: var(--border-radius-md);
    border: 1px solid rgba(197, 160, 89, 0.25);
    padding: var(--spacing-xl) var(--spacing-md);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    align-items: center;
    text-align: center;
    box-shadow: var(--shadow-soft);
}

.cover-header {
    margin-top: var(--spacing-md);
}

.cover-header h1 {
    font-family: var(--font-display);
    font-size: 2.8rem;
    font-weight: 400;
    color: var(--color-primary);
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
}

.flower-divider {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    margin-top: var(--spacing-sm);
}
.flower-divider .dot {
    width: 5px;
    height: 5px;
    background-color: var(--color-accent);
    border-radius: 50%;
}
.flower-divider .line {
    width: 60px;
    height: 1px;
    background-color: var(--color-accent);
}

.greeting-lead {
    font-family: var(--font-serif);
    font-size: 1.35rem;
    line-height: 1.6;
    color: var(--color-text-dark);
    max-width: 320px;
}

/* ==========================================================================
   Page 2: Letter Page (Paddings adjusted to frame layout)
   ========================================================================== */
#letter-page {
    background: url('../assets/letter-bg.png');
    background-size: cover;
    background-position: center;
    display: flex;
    flex-direction: column;
    padding: 2.8rem; /* Framing space outside border */
}

.letter-border {
    border: 1px solid rgba(197, 160, 89, 0.25);
    height: 100%;
    width: 100%;
    padding: var(--spacing-lg) 2.5rem; /* Inner padding from border to text */
    border-radius: var(--border-radius-md);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    background-color: rgba(255, 255, 255, 0.65);
}

.letter-title {
    font-family: var(--font-display);
    font-size: 1.95rem;
    font-weight: 400;
    color: var(--color-primary);
    margin-bottom: var(--spacing-sm);
}

.letter-body {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    line-height: 1.35;
    color: var(--color-text-dark);
    flex-grow: 1;
    overflow-y: auto;
    scrollbar-width: none; /* Hide scrollbar Firefox */
}

.letter-body::-webkit-scrollbar {
    display: none; /* Hide scrollbar Safari/Chrome */
}

.letter-body p {
    margin-bottom: var(--spacing-sm);
}

.letter-body .highlight-text {
    font-weight: 600;
    color: var(--color-primary);
}

.letter-signature {
    font-family: var(--font-serif);
    font-style: italic;
    font-size: 1.8rem;
    margin-top: var(--spacing-xs);
    color: var(--color-primary);
}

.letter-footer {
    display: flex;
    justify-content: space-between;
    gap: var(--spacing-md);
    margin-top: auto;
}

/* ==========================================================================
   Page 3: Cottage Comparison Page
   ========================================================================== */
#cottage-page {
    background-color: var(--color-bg-main);
    display: flex;
    flex-direction: column;
    padding: 0;
}

.cottage-container {
    height: 100%;
    display: flex;
    flex-direction: column;
}

.cottage-header {
    padding: var(--spacing-md) var(--spacing-md) var(--spacing-xs);
    background-color: var(--color-card-bg);
    border-bottom: 1px solid rgba(114, 47, 55, 0.05);
}

.cottage-header-nav {
    margin-bottom: var(--spacing-sm);
}

.cottage-header h2 {
    font-family: var(--font-display);
    font-size: 1.8rem;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xs);
}

.cottage-header p {
    font-family: var(--font-sans);
    color: var(--color-text-light);
    font-size: 0.9rem;
}

.cottage-list {
    flex-grow: 1;
    overflow-y: auto;
    padding: var(--spacing-md);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    scroll-behavior: smooth;
    
    scrollbar-width: thin;
    scrollbar-color: var(--color-primary-light) rgba(0,0,0,0.02);
}

.cottage-list::-webkit-scrollbar {
    width: 5px;
}
.cottage-list::-webkit-scrollbar-track {
    background: rgba(0, 0, 0, 0.02);
}
.cottage-list::-webkit-scrollbar-thumb {
    background-color: var(--color-primary-light);
    border-radius: 10px;
}

.cottage-card {
    background-color: var(--color-card-bg);
    border-radius: var(--border-radius-md);
    border: 1px solid rgba(114, 47, 55, 0.06);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-soft);
    transition: transform var(--transition-hover), box-shadow var(--transition-hover), border-color var(--transition-hover);
}

.cottage-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-medium);
    border-color: rgba(197, 160, 89, 0.3);
}

.cottage-card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    border-bottom: 1px solid rgba(114, 47, 55, 0.05);
    padding-bottom: var(--spacing-xs);
    margin-bottom: var(--spacing-sm);
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.cottage-card-header h3 {
    font-family: var(--font-display);
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--color-primary);
}

.cottage-card-header .location {
    font-family: var(--font-sans);
    font-size: 0.8rem;
    font-weight: 400;
    color: var(--color-text-light);
    display: block;
    margin-top: 2px;
}

.style-badge {
    background-color: rgba(197, 160, 89, 0.08);
    color: var(--color-primary);
    border: 1px solid rgba(197, 160, 89, 0.15);
    font-size: 0.72rem;
    font-weight: 500;
    padding: 2px 8px;
    border-radius: 20px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.cottage-card-body {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.pro-con h4 {
    font-family: var(--font-sans);
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 4px;
}

.pro-con.advantages h4 {
    color: var(--color-success);
}
.pro-con.disadvantages h4 {
    color: var(--color-warning);
}

.pro-con ul {
    list-style: none;
}

.pro-con ul li {
    font-family: var(--font-sans);
    font-size: 0.84rem;
    line-height: 1.4;
    color: var(--color-text-light);
    margin-bottom: 4px;
    position: relative;
    padding-left: 12px;
}

.pro-con.advantages ul li::before {
    content: '•';
    color: var(--color-success);
    position: absolute;
    left: 0;
}

.pro-con.disadvantages ul li::before {
    content: '•';
    color: var(--color-warning);
    position: absolute;
    left: 0;
}

.cottage-card-footer {
    display: flex;
    justify-content: flex-end;
}

/* ==========================================================================
   Buttons and Micro-Interactions
   ========================================================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    font-family: var(--font-sans);
    font-size: 0.9rem;
    font-weight: 500;
    padding: 10px 24px;
    border-radius: var(--border-radius-md);
    cursor: pointer;
    border: none;
    outline: none;
    transition: background-color var(--transition-hover), transform var(--transition-hover), box-shadow var(--transition-hover);
}

.btn-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    line-height: 1;
}

.btn-icon svg {
    display: block;
}

.btn-primary {
    background-color: var(--color-primary);
    color: var(--color-card-bg);
    box-shadow: 0 4px 12px rgba(114, 47, 55, 0.15);
}

.btn-primary:hover {
    background-color: #5d242a;
    transform: translateY(-2px);
    box-shadow: 0 6px 18px rgba(114, 47, 55, 0.25);
}

.btn-secondary {
    background-color: transparent;
    color: var(--color-text-light);
    border: 1px solid rgba(114, 47, 55, 0.15);
}

.btn-secondary:hover {
    background-color: rgba(114, 47, 55, 0.05);
    color: var(--color-primary);
}

.btn-sm {
    padding: 8px 16px;
    font-size: 0.82rem;
}

.btn-text-link {
    background: none;
    border: none;
    color: var(--color-accent);
    font-size: 0.82rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 4px;
    text-decoration: none;
    padding: 4px 8px;
    border-radius: var(--border-radius-sm);
    transition: color var(--transition-hover), background-color var(--transition-hover);
}

.btn-text-link:hover {
    color: var(--color-primary);
    background-color: rgba(114, 47, 55, 0.03);
}

.corner-peel-hint {
    position: absolute;
    bottom: 0;
    right: 0;
    width: 45px;
    height: 45px;
    background: linear-gradient(135deg, transparent 45%, rgba(0, 0, 0, 0.08) 50%, rgba(255, 255, 255, 0.95) 55%, rgba(197, 160, 89, 0.15) 80%);
    box-shadow: -2px -2px 5px rgba(0, 0, 0, 0.03);
    cursor: pointer;
    border-radius: 0 0 var(--border-radius-lg) 0;
    transition: width var(--transition-hover), height var(--transition-hover);
    z-index: 10;
}

.page.front:hover .corner-peel-hint {
    width: 60px;
    height: 60px;
}

/* ==========================================================================
   Responsive Overrides (Flipped Center-Shift for Mobile Layouts)
   ========================================================================== */
@media (min-width: 769px) {
    .cottage-card-body {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 950px) {
    /* Soften the 3D perspective distortion on mobile */
    .viewport {
        perspective: 3000px;
    }

    .book {
        width: 900px;
        height: 650px;
        --book-scale: clamp(0.5, 92vw / 450px, 0.95);
        transform: scale(var(--book-scale)) translateX(var(--book-translate-x));
        transform-origin: center center;
    }

    .book::before {
        display: none;
    }

    /* Retain 50% width and left 50% spine position on mobile for exact 3D flip physics! */
    .sheet {
        left: 50%;
        width: 50%;
        transform-origin: left center;
    }

    /* Restore original asymmetric border-radii to preserve precise layout boundaries */
    .page {
        border-radius: 0 var(--border-radius-lg) var(--border-radius-lg) 0;
    }

    .page.back {
        border-radius: var(--border-radius-lg) 0 0 var(--border-radius-lg);
    }
    
    /* Sheet 1 transition transforms */
    #sheet-1 {
        transform-style: preserve-3d;
        z-index: 10;
        transition: transform var(--transition-peel), opacity 0.5s ease, visibility 0s linear;
    }

    #sheet-1.flipped {
        transform: rotateY(-180deg) translateX(0);
        opacity: 1;
        pointer-events: auto;
    }

    /* Page 2 -> Page 3 Transition: Slide the flipped sheet left in its local coordinate space */
    #sheet-1.flipped.step-3 {
        transform: rotateY(-180deg) translateX(150%);
        opacity: 0;
        pointer-events: none;
    }
    
    /* Sheet 2 layout: static and centered underneath */
    #sheet-2 {
        z-index: 8;
    }

    /* Dynamic book translation to center active step page */
    .book.state-1 {
        --book-translate-x: -25%; /* Cover page centers */
    }
    .book.state-2 {
        --book-translate-x: 25%;  /* Left page (Letter) centers */
    }
    .book.state-3 {
        --book-translate-x: -25%; /* Right page (Cottages) centers */
    }

    /* WebKit 3D Depth Layer visibility rules customized for mobile states */
    .book.state-1 #sheet-1 {
        visibility: visible;
        transition-delay: 0s;
    }
    .book.state-1 #sheet-2 {
        visibility: hidden;
        transition-delay: 1.2s;
    }
    .book.state-2 #sheet-1 {
        visibility: visible;
        transition-delay: 0s;
    }
    .book.state-2 #sheet-2 {
        visibility: hidden;
        transition-delay: 1.2s;
    }
    .book.state-3 #sheet-1 {
        visibility: hidden;
        transition-delay: 1.2s;
    }
    .book.state-3 #sheet-2 {
        visibility: visible;
        transition-delay: 0s;
    }
}

@media (max-width: 520px) {
    .cover-card {
        padding: var(--spacing-md) var(--spacing-sm);
    }
    
    .cover-header h1 {
        font-size: 2.8rem; /* Font sizes raised to compensate for --book-scale factor */
    }
    
    .greeting-lead {
        font-size: 1.45rem;
    }

    #letter-page {
        padding: 2.8rem; /* 10% smaller relative padding on mobile letter */
    }

    .letter-border {
        padding: var(--spacing-lg) 2.5rem; /* Expanded text margins */
    }

    .letter-title {
        font-size: 2.1rem;
        margin-bottom: var(--spacing-xs);
    }

    .letter-body {
        font-size: 1.45rem; /* Raised to visually output a comfortable 18px size */
        line-height: 1.35;
    }
    
    .letter-body p {
        margin-bottom: 8px;
    }

    .letter-signature {
        font-size: 2rem;
        margin-top: var(--spacing-xs);
    }
    
    .btn {
        padding: 8px 16px;
        font-size: 0.8rem;
    }
}