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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    max-width: 450px;
    width: 100%;
    overflow: hidden;
}

.header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 40px 30px;
    text-align: center;
}

.header h1 {
    font-size: 1.8em;
    margin-bottom: 10px;
}

.header p {
    opacity: 0.9;
}

.form-container {
    padding: 40px 30px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    color: #333;
    font-weight: 500;
}

.form-group input {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid #e0e0e0;
    border-radius: 10px;
    font-size: 1em;
    transition: border-color 0.3s;
}

.form-group input:focus {
    outline: none;
    border-color: #667eea;
}

.form-group input.error {
    border-color: #f44336;
}

.form-group .helper-text {
    font-size: 0.85em;
    color: #666;
    margin-top: 5px;
}

.form-group .error-text {
    font-size: 0.85em;
    color: #f44336;
    margin-top: 5px;
    display: none;
}

.form-group input.error + .error-text {
    display: block;
}

.btn {
    width: 100%;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    padding: 15px;
    font-size: 1.1em;
    border-radius: 10px;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
    margin-bottom: 15px;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

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

.btn:disabled {
    background: #ccc;
    cursor: not-allowed;
    box-shadow: none;
    transform: none;
}

.btn-secondary {
    background: white;
    color: #667eea;
    border: 2px solid #667eea;
    box-shadow: none;
}

.btn-secondary:hover {
    background: #f8f9fa;
}

.error {
    background: #fee;
    color: #c33;
    padding: 12px;
    border-radius: 8px;
    margin-bottom: 20px;
    display: none;
    text-align: center;
}

.error.show {
    display: block;
    animation: fadeIn 0.3s;
}

.success {
    background: #d4edda;
    color: #155724;
    padding: 12px;
    border-radius: 8px;
    margin-bottom: 20px;
    display: none;
    text-align: center;
}

.success.show {
    display: block;
    animation: fadeIn 0.3s;
}

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

.info-text {
    text-align: center;
    color: #666;
    font-size: 0.9em;
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid #e0e0e0;
}

.link-text {
    color: #667eea;
    cursor: pointer;
    text-decoration: none;
}

.link-text:hover {
    text-decoration: underline;
}

.demo-credentials {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 10px;
    margin-top: 20px;
    font-size: 0.85em;
}

.demo-credentials h3 {
    color: #667eea;
    margin-bottom: 10px;
    font-size: 1em;
}

.demo-credentials p {
    margin: 5px 0;
    color: #555;
}

.demo-credentials strong {
    color: #333;
}

.password-strength {
    margin-top: 5px;
    height: 4px;
    background: #e0e0e0;
    border-radius: 2px;
    overflow: hidden;
}

.password-strength-bar {
    height: 100%;
    width: 0;
    transition: width 0.3s, background 0.3s;
}

.password-strength-bar.weak {
    width: 33%;
    background: #f44336;
}

.password-strength-bar.medium {
    width: 66%;
    background: #ff9800;
}

.password-strength-bar.strong {
    width: 100%;
    background: #4caf50;
}