/* ============================================
   CSS RESET & VARIABLES
   ============================================ */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
    --bg-primary: #0a0a0f;
    --bg-secondary: #12121a;
    --bg-card: #16161f;
    --bg-code: #1a1a2e;
    --text-primary: #e8e8f0;
    --text-secondary: #9595a8;
    --text-muted: #5a5a70;
    --border: #2a2a3a;

    /* SOLID Colors */
    --s-color: #f472b6;
    --s-glow: #f472b640;
    --o-color: #818cf8;
    --o-glow: #818cf840;
    --l-color: #34d399;
    --l-glow: #34d39940;
    --i-color: #fbbf24;
    --i-glow: #fbbf2440;
    --d-color: #38bdf8;
    --d-glow: #38bdf840;

    --radius: 16px;
    --radius-sm: 8px;
    --font-sans: 'Inter', 'Space Grotesk', system-ui, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
}

html { scroll-behavior: smooth; }

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: hidden;
}

/* ============================================
   ANIMATED BACKGROUND
   ============================================ */
.bg-grid {
    position: fixed;
    inset: 0;
    z-index: 0;
    background-image:
        linear-gradient(rgba(255,255,255,.02) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255,255,255,.02) 1px, transparent 1px);
    background-size: 60px 60px;
    mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, black 40%, transparent 100%);
}

.bg-gradient-orbs {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    overflow: hidden;
}

.bg-gradient-orbs::before,
.bg-gradient-orbs::after {
    content: '';
    position: absolute;
    border-radius: 50%;
    filter: blur(120px);
    opacity: 0.15;
    animation: float 20s ease-in-out infinite;
}

.bg-gradient-orbs::before {
    width: 600px; height: 600px;
    background: var(--s-color);
    top: -200px; left: -100px;
}

.bg-gradient-orbs::after {
    width: 500px; height: 500px;
    background: var(--d-color);
    bottom: -200px; right: -100px;
    animation-delay: -10s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(30px, -30px) scale(1.05); }
    66% { transform: translate(-20px, 20px) scale(0.95); }
}

/* ============================================
   LAYOUT
   ============================================ */
.container {
    position: relative;
    z-index: 1;
    max-width: 960px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ============================================
   HERO SECTION
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 60px 0;
}

.hero-content {
    animation: fadeUp 1s ease-out;
}

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(40px); }
    to { opacity: 1; transform: translateY(0); }
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 20px;
    border-radius: 100px;
    border: 1px solid var(--border);
    background: var(--bg-secondary);
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    margin-bottom: 32px;
    backdrop-filter: blur(10px);
}

.hero-badge .dot {
    width: 8px; height: 8px;
    border-radius: 50%;
    background: var(--l-color);
    animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; box-shadow: 0 0 0 0 var(--l-glow); }
    50% { opacity: 0.7; box-shadow: 0 0 0 8px transparent; }
}

.hero h1 {
    font-family: 'Space Grotesk', var(--font-sans);
    font-size: clamp(3.5rem, 8vw, 7rem);
    font-weight: 900;
    line-height: 1;
    letter-spacing: -0.04em;
    margin-bottom: 8px;
}

.hero h1 .letter {
    display: inline-block;
    transition: transform 0.3s, color 0.3s;
    cursor: default;
}

.hero h1 .letter:hover {
    transform: translateY(-8px) scale(1.1);
}

.hero h1 .letter-s { color: var(--s-color); }
.hero h1 .letter-o { color: var(--o-color); }
.hero h1 .letter-l { color: var(--l-color); }
.hero h1 .letter-i { color: var(--i-color); }
.hero h1 .letter-d { color: var(--d-color); }

.hero h1 .letter-s:hover { text-shadow: 0 0 40px var(--s-glow); }
.hero h1 .letter-o:hover { text-shadow: 0 0 40px var(--o-glow); }
.hero h1 .letter-l:hover { text-shadow: 0 0 40px var(--l-glow); }
.hero h1 .letter-i:hover { text-shadow: 0 0 40px var(--i-glow); }
.hero h1 .letter-d:hover { text-shadow: 0 0 40px var(--d-glow); }

.hero-subtitle {
    font-size: clamp(1rem, 2.5vw, 1.35rem);
    color: var(--text-secondary);
    font-weight: 300;
    margin-bottom: 48px;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-subtitle strong {
    color: var(--text-primary);
    font-weight: 600;
}

.hero-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    justify-content: center;
}

.hero-nav a {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    border-radius: 12px;
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-primary);
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 600;
    transition: all 0.3s ease;
    backdrop-filter: blur(10px);
}

.hero-nav a:hover {
    transform: translateY(-2px);
    border-color: var(--text-muted);
    box-shadow: 0 8px 32px rgba(0,0,0,.3);
}

.hero-nav a .nav-letter {
    width: 28px; height: 28px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'Space Grotesk', var(--font-sans);
    font-weight: 800;
    font-size: 0.95rem;
}

.nav-s .nav-letter { background: var(--s-glow); color: var(--s-color); }
.nav-o .nav-letter { background: var(--o-glow); color: var(--o-color); }
.nav-l .nav-letter { background: var(--l-glow); color: var(--l-color); }
.nav-i .nav-letter { background: var(--i-glow); color: var(--i-color); }
.nav-d .nav-letter { background: var(--d-glow); color: var(--d-color); }

.nav-s:hover { border-color: var(--s-color) !important; box-shadow: 0 8px 32px var(--s-glow) !important; }
.nav-o:hover { border-color: var(--o-color) !important; box-shadow: 0 8px 32px var(--o-glow) !important; }
.nav-l:hover { border-color: var(--l-color) !important; box-shadow: 0 8px 32px var(--l-glow) !important; }
.nav-i:hover { border-color: var(--i-color) !important; box-shadow: 0 8px 32px var(--i-glow) !important; }
.nav-d:hover { border-color: var(--d-color) !important; box-shadow: 0 8px 32px var(--d-glow) !important; }

/* ============================================
   SCROLL INDICATOR
   ============================================ */
.scroll-indicator {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    color: var(--text-muted);
    font-size: 0.75rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    animation: fadeUp 1s ease-out 0.5s both;
}

.scroll-indicator .mouse {
    width: 24px; height: 40px;
    border: 2px solid var(--text-muted);
    border-radius: 12px;
    position: relative;
}

.scroll-indicator .mouse::after {
    content: '';
    width: 4px; height: 8px;
    background: var(--text-muted);
    border-radius: 2px;
    position: absolute;
    top: 8px;
    left: 50%;
    transform: translateX(-50%);
    animation: scrollWheel 2s ease-in-out infinite;
}

@keyframes scrollWheel {
    0%, 100% { opacity: 1; transform: translateX(-50%) translateY(0); }
    50% { opacity: 0.3; transform: translateX(-50%) translateY(10px); }
}

/* ============================================
   PRINCIPLE SECTION
   ============================================ */
.principle {
    padding: 100px 0 60px;
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease, transform 0.8s ease;
}

.principle.visible {
    opacity: 1;
    transform: translateY(0);
}

.principle-header {
    display: flex;
    align-items: center;
    gap: 20px;
    margin-bottom: 32px;
}

.principle-icon {
    width: 72px;
    height: 72px;
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'Space Grotesk', var(--font-sans);
    font-weight: 900;
    font-size: 2rem;
    flex-shrink: 0;
    position: relative;
}

.principle-icon::after {
    content: '';
    position: absolute;
    inset: -2px;
    border-radius: 22px;
    z-index: -1;
    opacity: 0.5;
    filter: blur(12px);
}

.principle-title-group h2 {
    font-family: 'Space Grotesk', var(--font-sans);
    font-size: clamp(1.8rem, 4vw, 2.5rem);
    font-weight: 800;
    line-height: 1.1;
    letter-spacing: -0.02em;
}

.principle-title-group .principle-fullname {
    font-size: 0.95rem;
    font-weight: 400;
    color: var(--text-secondary);
    margin-top: 4px;
}

.principle-desc {
    font-size: 1.1rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin-bottom: 36px;
    line-height: 1.8;
}

.principle-desc strong {
    color: var(--text-primary);
    font-weight: 600;
}

/* Principle S */
#srp .principle-icon { background: var(--s-glow); color: var(--s-color); }
#srp .principle-icon::after { background: var(--s-color); }
#srp h2 { color: var(--s-color); }

/* Principle O */
#ocp .principle-icon { background: var(--o-glow); color: var(--o-color); }
#ocp .principle-icon::after { background: var(--o-color); }
#ocp h2 { color: var(--o-color); }

/* Principle L */
#lsp .principle-icon { background: var(--l-glow); color: var(--l-color); }
#lsp .principle-icon::after { background: var(--l-color); }
#lsp h2 { color: var(--l-color); }

/* Principle I */
#isp .principle-icon { background: var(--i-glow); color: var(--i-color); }
#isp .principle-icon::after { background: var(--i-color); }
#isp h2 { color: var(--i-color); }

/* Principle D */
#dip .principle-icon { background: var(--d-glow); color: var(--d-color); }
#dip .principle-icon::after { background: var(--d-color); }
#dip h2 { color: var(--d-color); }

/* ============================================
   CODE BLOCKS
   ============================================ */
.code-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 24px;
}

@media (max-width: 768px) {
    .code-grid { grid-template-columns: 1fr; }
}

.code-block {
    border-radius: var(--radius);
    border: 1px solid var(--border);
    background: var(--bg-code);
    overflow: hidden;
    transition: border-color 0.3s, box-shadow 0.3s;
}

.code-block:hover {
    border-color: var(--text-muted);
    box-shadow: 0 8px 40px rgba(0,0,0,.3);
}

.code-block-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 16px;
    border-bottom: 1px solid var(--border);
    background: rgba(255,255,255,.02);
}

.code-block-header .filename {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.code-block-header .tag {
    font-size: 0.7rem;
    font-weight: 700;
    padding: 3px 10px;
    border-radius: 100px;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.tag-bad { background: #ef444430; color: #f87171; }
.tag-good { background: #22c55e30; color: #4ade80; }

.code-block pre {
    padding: 20px;
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.82rem;
    line-height: 1.75;
    color: var(--text-primary);
}

.code-block pre code {
    font-family: inherit;
}

/* Syntax highlighting */
.kw { color: #c792ea; }     /* keywords */
.fn { color: #82aaff; }     /* functions / methods */
.cl { color: #ffcb6b; }     /* classes */
.st { color: #c3e88d; }     /* strings */
.cm { color: #546e7a; font-style: italic; }  /* comments */
.vr { color: #f78c6c; }     /* variables / properties */
.ty { color: #89ddff; }     /* types / interfaces */
.op { color: #89ddff; }     /* operators */
.nb { color: #f07178; }     /* numbers / booleans */

/* ============================================
   KEY INSIGHT BOX
   ============================================ */
.insight-box {
    display: flex;
    gap: 16px;
    padding: 20px 24px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    background: var(--bg-card);
    margin-top: 24px;
    align-items: flex-start;
}

.insight-box .icon {
    font-size: 1.5rem;
    flex-shrink: 0;
    line-height: 1.4;
}

.insight-box p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.insight-box p strong {
    color: var(--text-primary);
}

/* ============================================
   DIVIDER
   ============================================ */
.divider {
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--border), transparent);
    margin: 20px 0;
}

/* ============================================
   FOOTER
   ============================================ */
footer {
    text-align: center;
    padding: 60px 24px 40px;
    color: var(--text-muted);
    font-size: 0.85rem;
    position: relative;
    z-index: 1;
}

footer .solid-mini {
    font-family: 'Space Grotesk', var(--font-sans);
    font-weight: 800;
    font-size: 1rem;
    letter-spacing: 0.1em;
}

footer .solid-mini .fs { color: var(--s-color); }
footer .solid-mini .fo { color: var(--o-color); }
footer .solid-mini .fl { color: var(--l-color); }
footer .solid-mini .fi { color: var(--i-color); }
footer .solid-mini .fd { color: var(--d-color); }

/* ============================================
   SCROLLBAR
   ============================================ */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--bg-primary); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* Code block scrollbar */
.code-block pre::-webkit-scrollbar { height: 6px; }
.code-block pre::-webkit-scrollbar-track { background: transparent; }
.code-block pre::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes slideInLeft {
    from { opacity: 0; transform: translateX(-30px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes slideInRight {
    from { opacity: 0; transform: translateX(30px); }
    to { opacity: 1; transform: translateX(0); }
}

.principle.visible .code-grid > :first-child {
    animation: slideInLeft 0.6s ease-out 0.2s both;
}

.principle.visible .code-grid > :last-child {
    animation: slideInRight 0.6s ease-out 0.3s both;
}

.principle.visible .insight-box {
    animation: fadeUp 0.6s ease-out 0.4s both;
}

/* ============================================
   BACK TO TOP
   ============================================ */
.back-to-top {
    position: fixed;
    bottom: 28px;
    right: 28px;
    z-index: 100;
    width: 48px;
    height: 48px;
    border-radius: 14px;
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0;
    transform: translateY(20px);
    transition: all 0.3s ease;
    backdrop-filter: blur(16px);
    text-decoration: none;
    font-size: 1.2rem;
}

.back-to-top.show {
    opacity: 1;
    transform: translateY(0);
}

.back-to-top:hover {
    border-color: var(--text-muted);
    color: var(--text-primary);
    box-shadow: 0 4px 20px rgba(0,0,0,.4);
}

/* ============================================
   SIBLING PAGE LINK / TOP NAV
   ============================================ */
.top-nav {
    position: fixed;
    top: 24px;
    right: 24px;
    z-index: 100;
    display: flex;
    gap: 10px;
}

.sibling-link {
    position: static;
    padding: 10px 18px;
    border-radius: 12px;
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.82rem;
    font-weight: 600;
    backdrop-filter: blur(16px);
    transition: all 0.3s ease;
}

.sibling-link:hover {
    border-color: var(--text-muted);
    color: var(--text-primary);
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0,0,0,.3);
}