/* ===== Design Tokens ===== */
:root {
    --color-bg: #0a0a1a;
    --color-primary: #7c3aed;
    --color-primary-light: #a78bfa;
    --color-accent: #06b6d4;
    --color-accent-glow: rgba(6, 182, 212, 0.35);
    --color-text: #f1f5f9;
    --color-text-muted: #94a3b8;
    --color-glass: rgba(255, 255, 255, 0.06);
    --color-glass-border: rgba(255, 255, 255, 0.12);
    --font-main: 'Outfit', sans-serif;
    --radius-lg: 20px;
    --radius-md: 14px;
    --shadow-glow: 0 0 40px rgba(124, 58, 237, 0.25), 0 0 80px rgba(6, 182, 212, 0.1);
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    height: 100%;
    overflow: hidden;
}

body {
    font-family: var(--font-main);
    color: var(--color-text);
    background: var(--color-bg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    position: relative;
}

/* ===== Background ===== */
body::before {
    content: '';
    position: fixed;
    inset: 0;
    background: url('cuongbeo.jpg') center/cover no-repeat;
    z-index: 0;
}

.bg-overlay {
    position: fixed;
    inset: 0;
    background: linear-gradient(
        180deg,
        rgba(10, 10, 26, 0.55) 0%,
        rgba(10, 10, 26, 0.75) 50%,
        rgba(10, 10, 26, 0.90) 100%
    );
    z-index: 1;
}

/* ===== Particles ===== */
.particles {
    position: fixed;
    inset: 0;
    z-index: 2;
    pointer-events: none;
}

.particle {
    position: absolute;
    background: var(--color-accent);
    border-radius: 50%;
    opacity: 0;
    animation: float-particle linear infinite;
}

@keyframes float-particle {
    0% {
        opacity: 0;
        transform: translateY(0) scale(0.5);
    }
    20% {
        opacity: 0.6;
    }
    80% {
        opacity: 0.3;
    }
    100% {
        opacity: 0;
        transform: translateY(-120vh) scale(1.2);
    }
}

/* ===== Hero ===== */
.hero {
    position: relative;
    z-index: 3;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 28px;
    padding: 40px;
    animation: fadeInUp 1s ease-out both;
}

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

/* ===== Logo ===== */
.logo-container {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
}

.logo-glow {
    position: absolute;
    width: 280px;
    height: 80px;
    background: radial-gradient(ellipse, var(--color-accent-glow) 0%, transparent 70%);
    filter: blur(30px);
    animation: pulse-glow 3s ease-in-out infinite alternate;
}

@keyframes pulse-glow {
    from { opacity: 0.5; transform: scale(0.9); }
    to   { opacity: 1;   transform: scale(1.1); }
}

.logo-text {
    font-size: 3.6rem;
    font-weight: 800;
    letter-spacing: -1px;
    background: linear-gradient(135deg, var(--color-text) 30%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: none;
    position: relative;
}

.logo-text span {
    display: block;
    font-size: 1.6rem;
    font-weight: 600;
    letter-spacing: 8px;
    text-transform: uppercase;
    background: linear-gradient(135deg, var(--color-primary-light) 0%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-top: -4px;
}

/* ===== Tagline ===== */
.tagline {
    font-size: 1.1rem;
    color: var(--color-text-muted);
    font-weight: 400;
    letter-spacing: 0.5px;
    animation: fadeInUp 1s ease-out 0.3s both;
}

/* ===== Buttons ===== */
.btn-group {
    display: flex;
    flex-direction: column;
    gap: 16px;
    width: 100%;
    max-width: 340px;
    animation: fadeInUp 1s ease-out 0.6s both;
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 16px 32px;
    border-radius: var(--radius-md);
    font-family: var(--font-main);
    font-size: 1.05rem;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(255,255,255,0.1) 0%, transparent 50%);
    opacity: 0;
    transition: opacity 0.35s ease;
}

.btn:hover::before {
    opacity: 1;
}

.btn-icon {
    width: 20px;
    height: 20px;
    flex-shrink: 0;
}

/* Primary Button */
.btn-primary {
    background: linear-gradient(135deg, var(--color-primary) 0%, #5b21b6 50%, var(--color-accent) 100%);
    background-size: 200% 200%;
    color: #fff;
    border: 1px solid rgba(255, 255, 255, 0.15);
    box-shadow:
        0 4px 20px rgba(124, 58, 237, 0.35),
        0 0 60px rgba(124, 58, 237, 0.1);
    animation: gradient-shift 4s ease infinite;
}

@keyframes gradient-shift {
    0%, 100% { background-position: 0% 50%; }
    50%      { background-position: 100% 50%; }
}

.btn-primary:hover {
    transform: translateY(-3px) scale(1.02);
    box-shadow:
        0 8px 30px rgba(124, 58, 237, 0.5),
        0 0 80px rgba(124, 58, 237, 0.2);
}

.btn-primary:active {
    transform: translateY(0) scale(0.98);
}

/* Secondary Button */
.btn-secondary {
    background: var(--color-glass);
    color: var(--color-text);
    border: 1px solid var(--color-glass-border);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: rgba(255, 255, 255, 0.2);
    transform: translateY(-3px) scale(1.02);
    box-shadow: 0 8px 30px rgba(6, 182, 212, 0.15);
}

.btn-secondary:active {
    transform: translateY(0) scale(0.98);
}

/* ===== Footer ===== */
.footer {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 3;
    text-align: center;
    padding: 20px;
    font-size: 0.8rem;
    color: var(--color-text-muted);
    opacity: 0.5;
}

/* ===== Responsive ===== */
@media (max-width: 480px) {
    .logo-text {
        font-size: 2.6rem;
    }
    .logo-text span {
        font-size: 1.2rem;
        letter-spacing: 5px;
    }
    .hero {
        padding: 24px;
    }
    .btn-group {
        max-width: 100%;
    }
    .btn {
        padding: 14px 24px;
        font-size: 0.95rem;
    }
}