:root {
    --primary-color: #0f172a;
    --accent-color: #2563eb;
    --accent-hover: #1d4ed8;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --error-color: #ef4444;
    --success-color: #10b981;
    --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: 20px;
}

.auth-container {
    background: var(--card-bg);
    width: 100%;
    max-width: 420px;
    padding: 2.5rem;
    border-radius: 16px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

.auth-header {
    text-align: center;
    margin-bottom: 2rem;
}

.auth-header h1 {
    font-size: 1.75rem;
    font-weight: 800;
    color: var(--primary-color);
    letter-spacing: -0.025em;
    margin-bottom: 0.5rem;
}

.auth-header p {
    color: var(--text-muted);
    font-size: 0.875rem;
}

.auth-tabs {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    padding: 4px;
    background: var(--bg-color);
    border-radius: 12px;
}

.tab-btn {
    flex: 1;
    padding: 0.75rem;
    border: none;
    background: transparent;
    color: var(--text-muted);
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
    border-radius: 8px;
    transition: var(--transition);
}

.tab-btn.active {
    background: var(--card-bg);
    color: var(--primary-color);
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.auth-form {
    display: none;
    flex-direction: column;
    gap: 1.25rem;
}

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

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

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

.form-group label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-main);
}

.form-group input {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    outline: none;
    font-size: 1rem;
    transition: var(--transition);
}

.form-group input:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
}

.btn-submit {
    margin-top: 0.5rem;
    padding: 0.875rem;
    background: var(--accent-color);
    color: white;
    border: none;
    border-radius: 10px;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
}

.btn-submit:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

.btn-submit:active {
    transform: translateY(0);
}

.alert {
    padding: 0.75rem 1rem;
    border-radius: 10px;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 1.5rem;
    display: none;
}

.alert-error {
    background: #fef2f2;
    color: var(--error-color);
    border: 1px solid #fee2e2;
}

.alert-success {
    background: #f0fdf4;
    color: var(--success-color);
    border: 1px solid #dcfce7;
}

@media (max-width: 480px) {
    .auth-container {
        padding: 1.5rem;
    }
}