:root {
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --bg-dark: #0f172a;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --glass-bg: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Inter', sans-serif;
}

body {
    background-color: var(--bg-dark);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    position: relative;
}

/* Dynamic Animated Background */
.background-animation {
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle at 50% 50%, rgba(99, 102, 241, 0.15), transparent 40%),
                radial-gradient(circle at 80% 20%, rgba(236, 72, 153, 0.1), transparent 30%);
    animation: rotate 30s linear infinite;
    z-index: 0;
}

@keyframes rotate {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.container {
    position: relative;
    z-index: 1;
    width: 100%;
    max-width: 400px;
    padding: 20px;
}

/* Glassmorphism Panel */
.glass-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: 20px;
    padding: 2rem;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    animation: floatIn 0.8s ease-out;
}

@keyframes floatIn {
    0% { opacity: 0; transform: translateY(20px); }
    100% { opacity: 1; transform: translateY(0); }
}

.tab-header {
    display: flex;
    margin-bottom: 2rem;
    border-bottom: 1px solid var(--glass-border);
}

.tab-header button {
    flex: 1;
    background: none;
    border: none;
    color: var(--text-muted);
    padding: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    border-bottom: 2px solid transparent;
}

.tab-header button.active {
    color: var(--primary);
    border-bottom: 2px solid var(--primary);
}

.auth-form {
    display: none;
    flex-direction: column;
    gap: 1.2rem;
}

.auth-form.active {
    display: flex;
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    0% { opacity: 0; }
    100% { opacity: 1; }
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.input-group label {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.input-group input {
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 12px 16px;
    border-radius: 10px;
    font-size: 1rem;
    outline: none;
    transition: all 0.3s ease;
}

.input-group input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.2);
}

.btn-primary {
    background: var(--primary);
    color: white;
    border: none;
    padding: 14px;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 0.5rem;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 10px 15px -3px rgba(99, 102, 241, 0.3);
}

.alert {
    padding: 12px;
    border-radius: 8px;
    margin-bottom: 1rem;
    font-size: 0.9rem;
    text-align: center;
}

.alert.hidden {
    display: none;
}

.alert.error {
    background: rgba(239, 68, 68, 0.1);
    color: #fca5a5;
    border: 1px solid rgba(239, 68, 68, 0.2);
}

.alert.success {
    background: rgba(34, 197, 94, 0.1);
    color: #86efac;
    border: 1px solid rgba(34, 197, 94, 0.2);
}