@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

:root {
    /* Light theme - rực rỡ, sống động, không nhàm chán */
    --bg-light: linear-gradient(-45deg, #ff9a9e, #fecfef, #a1c4fd, #c2e9fb);
    --card-bg-light: rgba(255, 255, 255, 0.45); /* Trong suốt hơn để thấy nền */
    --text-primary-light: #1e293b;
    --text-secondary-light: #475569;
    --border-light: rgba(255, 255, 255, 0.7);
    --shadow-light: 0 30px 60px -15px rgba(0, 0, 0, 0.15), 0 0 0 1px rgba(255, 255, 255, 0.5);
    --glow-primary-light: #6366f1;
    --glow-secondary-light: #ec4899;
    --accent-gradient-light: linear-gradient(135deg, #6366f1, #ec4899);
    --hover-glow-light: rgba(99, 102, 241, 0.4);
    --panel-bg-light: rgba(255, 255, 255, 0.55);

    /* Dark theme - sâu, huyền bí, dải ngân hà */
    --bg-dark: linear-gradient(-45deg, #0f172a, #1e1b4b, #170f3f, #020617);
    --card-bg-dark: rgba(15, 23, 42, 0.45);
    --text-primary-dark: #f8fafc;
    --text-secondary-dark: #94a3b8;
    --border-dark: rgba(255, 255, 255, 0.15);
    --shadow-dark: 0 30px 60px -15px rgba(0, 0, 0, 0.8), 0 0 0 1px rgba(255, 255, 255, 0.1);
    --glow-primary-dark: #00f2fe;
    --glow-secondary-dark: #4facfe;
    --accent-gradient-dark: linear-gradient(135deg, #00f2fe, #4facfe);
    --hover-glow-dark: rgba(0, 242, 254, 0.4);
    --panel-bg-dark: rgba(30, 41, 59, 0.4);

    /* Mặc định light */
    --bg: var(--bg-light);
    --card-bg: var(--card-bg-light);
    --text-primary: var(--text-primary-light);
    --text-secondary: var(--text-secondary-light);
    --border: var(--border-light);
    --shadow: var(--shadow-light);
    --glow-primary: var(--glow-primary-light);
    --glow-secondary: var(--glow-secondary-light);
    --accent-gradient: var(--accent-gradient-light);
    --hover-glow: var(--hover-glow-light);
    --panel-bg: var(--panel-bg-light);
}

.dark-mode {
    --bg: var(--bg-dark);
    --card-bg: var(--card-bg-dark);
    --text-primary: var(--text-primary-dark);
    --text-secondary: var(--text-secondary-dark);
    --border: var(--border-dark);
    --shadow: var(--shadow-dark);
    --glow-primary: var(--glow-primary-dark);
    --glow-secondary: var(--glow-secondary-dark);
    --accent-gradient: var(--accent-gradient-dark);
    --hover-glow: var(--hover-glow-dark);
    --panel-bg: var(--panel-bg-dark);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg);
    background-size: 400% 400%;
    animation: gradientBG 15s ease infinite;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    color: var(--text-primary);
    line-height: 1.6;
    padding: 1rem;
    transition: color 0.3s ease;
    position: relative;
    overflow-x: hidden;
}

@keyframes gradientBG {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

/* Overlay khởi động */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--bg);
    z-index: 10000;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    backdrop-filter: blur(10px);
    transition: opacity 0.4s ease;
}

.loader {
    position: relative;
    width: 100px;
    height: 100px;
    margin-bottom: 30px;
}

.ring {
    position: absolute;
    width: 100%;
    height: 100%;
    border-radius: 50%;
    border: 3px solid transparent;
    border-top-color: var(--glow-primary);
    border-bottom-color: var(--glow-secondary);
    animation: spin 1.2s cubic-bezier(0.68, -0.55, 0.27, 1.55) infinite;
}

.ring.inner {
    width: 70%;
    height: 70%;
    top: 15%;
    left: 15%;
    border-top-color: var(--glow-secondary);
    border-bottom-color: var(--glow-primary);
    animation-direction: reverse;
    animation-duration: 0.8s;
}

@keyframes spin {
    100% { transform: rotate(360deg); }
}

.glitch-text {
    font-size: 24px;
    font-weight: 800;
    letter-spacing: 8px;
    color: var(--glow-primary);
    position: relative;
    text-transform: uppercase;
    animation: glitch 3s infinite;
}

.glitch-text::before,
.glitch-text::after {
    content: attr(data-text);
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0.6;
}
.glitch-text::before {
    color: var(--glow-secondary);
    z-index: -1;
    animation: glitchOffset 0.3s infinite;
}
.glitch-text::after {
    color: var(--glow-primary);
    z-index: -2;
    animation: glitchOffset 0.2s infinite reverse;
}

@keyframes glitchOffset {
    0% { transform: translate(0); }
    20% { transform: translate(-2px, 1px); }
    40% { transform: translate(2px, -1px); }
    60% { transform: translate(-1px, 2px); }
    80% { transform: translate(1px, -2px); }
    100% { transform: translate(0); }
}

.tap-pulse {
    color: var(--text-secondary);
    font-size: 14px;
    letter-spacing: 3px;
    margin-top: 25px;
    animation: pulseFade 2s infinite;
    border: 1px solid var(--border);
    padding: 10px 28px;
    border-radius: 40px;
    backdrop-filter: blur(5px);
    background: var(--panel-bg);
}

@keyframes pulseFade {
    0%, 100% { opacity: 0.7; box-shadow: 0 0 15px var(--glow-primary); }
    50% { opacity: 1; box-shadow: 0 0 30px var(--glow-primary); }
}

/* Scrollbar */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--panel-bg); border-radius: 10px; }
::-webkit-scrollbar-thumb { background: var(--accent-gradient); border-radius: 10px; }

/* Theme toggle */
.theme-toggle-container {
    position: absolute;
    top: 20px;
    right: 20px;
    z-index: 1000;
}

.theme-toggle {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--panel-bg);
    border: 1px solid var(--border);
    backdrop-filter: blur(10px);
    color: var(--text-primary);
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.theme-toggle:hover {
    transform: scale(1.1) rotate(15deg);
    box-shadow: 0 0 25px var(--hover-glow);
    border-color: transparent;
}

.theme-toggle i {
    position: absolute;
    transition: opacity 0.3s, transform 0.3s;
}

.theme-toggle .fa-sun {
    opacity: 1;
    transform: scale(1);
}

.theme-toggle .fa-moon {
    opacity: 0;
    transform: scale(0.5);
}

.dark-mode .theme-toggle .fa-sun {
    opacity: 0;
    transform: scale(0.5);
}

.dark-mode .theme-toggle .fa-moon {
    opacity: 1;
    transform: scale(1);
}

/* Heart pop */
.heart-pop {
    position: fixed;
    font-size: 28px;
    color: var(--glow-secondary);
    pointer-events: none;
    z-index: 9999;
    animation: heartLaser 1.2s ease-out forwards;
    text-shadow: 0 0 20px var(--glow-secondary);
}

@keyframes heartLaser {
    0% { transform: translate(0,0) scale(1) rotate(0deg); opacity: 1; }
    100% { transform: translate(var(--x), calc(var(--y) - 180px)) scale(0.2) rotate(720deg); opacity: 0; }
}

/* Reveal animation */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s cubic-bezier(0.2, 0.9, 0.3, 1), transform 0.8s cubic-bezier(0.2, 0.9, 0.3, 1);
}

.reveal.active {
    opacity: 1;
    transform: translateY(0);
}

/* Ripple effect */
.ripple-effect {
    position: absolute;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.5);
    transform: scale(0);
    animation: ripple 0.7s linear;
    pointer-events: none;
}

@keyframes ripple {
    to {
        transform: scale(5);
        opacity: 0;
    }
}

/* Mouse Trail */
.cursor-trail {
    position: fixed;
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--accent-gradient);
    box-shadow: 0 0 12px var(--glow-primary), 0 0 24px var(--glow-secondary);
    pointer-events: none;
    z-index: 9999;
    transform: translate(-50%, -50%);
    animation: fadeAndShrink 0.6s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
}
@keyframes fadeAndShrink {
    0% { opacity: 1; transform: translate(-50%, -50%) scale(1.2); }
    100% { opacity: 0; transform: translate(-50%, -50%) scale(0.1); }
}