:root {
    --primary: #3498db;
    --primary-hover: #2980b9;
    --bg-color: #f7f9fa;
    --card-bg: #ffffff;
    --text-main: #2c3e50;
    --text-muted: #7f8c8d;
    --border-color: #ecf0f1;
}

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

body {
    font-family: 'Apple SD Gothic Neo', 'Malgun Gothic', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    -webkit-font-smoothing: antialiased;
}

/* Utility */
.w-100 {
    width: 100%;
}

.text-center {
    text-align: center;
}

.text-muted {
    color: var(--text-muted);
}

.text-danger {
    color: #e74c3c;
}

.small {
    font-size: 0.85rem;
}

.mt-2 {
    margin-top: 10px;
}

/* Buttons */
.btn {
    border: none;
    padding: 12px 15px;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
    font-size: 1rem;
    font-weight: 600;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.primary-btn {
    background-color: var(--primary);
    color: white;
}

.primary-btn:hover:not(:disabled) {
    background-color: var(--primary-hover);
}

/* Layout Containers */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

.mobile-container {
    max-width: 480px;
    margin: 0 auto;
    min-height: 100vh;
    background: var(--bg-color);
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.02);
}

.card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 25px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.03);
    border: 1px solid rgba(0, 0, 0, 0.05);
}

/* Auth Layout */
.auth-container {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: 20px;
}

.auth-container .card {
    width: 100%;
    max-width: 400px;
}

.logo {
    text-align: center;
    margin-bottom: 25px;
    font-size: 1.8rem;
    color: var(--primary);
    letter-spacing: -0.5px;
}

.tabs {
    display: flex;
    border-bottom: 2px solid var(--border-color);
    margin-bottom: 25px;
}

.tab-btn {
    flex: 1;
    background: none;
    border: none;
    padding: 12px;
    cursor: pointer;
    font-size: 1.05rem;
    color: var(--text-muted);
    font-weight: bold;
    transition: color 0.2s;
}

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

.auth-form {
    display: none;
}

.auth-form.active-form {
    display: block;
    animation: fadeIn 0.3s;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(5px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.input-group {
    margin-bottom: 18px;
}

.input-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    font-size: 0.9rem;
    color: #34495e;
}

.input-group input {
    width: 100%;
    border: 1px solid #bdc3c7;
    padding: 12px;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.2s;
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(52, 152, 219, 0.2);
}

/* App Header */
.app-header {
    background: var(--card-bg);
    padding: 15px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

.app-header h2 {
    font-size: 1.25rem;
    margin: 0;
    color: var(--primary);
    letter-spacing: -0.5px;
}

.logout-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
}

.logout-btn:hover {
    color: #e74c3c;
}

.app-content {
    padding: 20px;
}