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

        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Helvetica Neue", Arial, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 20px;
            line-height: 1.6;
        }

        .container {
            background: rgba(255, 255, 255, 0.95);
            backdrop-filter: blur(10px);
            border-radius: 20px;
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
            overflow: hidden;
            width: 100%;
            max-width: 500px;
            padding: 0;
        }

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

        .header::before {
            content: '';
            position: absolute;
            bottom: 0;
            left: 50%;
            transform: translateX(-50%);
            width: 60px;
            height: 4px;
            background: rgba(255, 255, 255, 0.3);
            border-radius: 2px;
        }

        .header h1 {
            font-size: 2em;
            margin-bottom: 10px;
            font-weight: 700;
        }

        .header p {
            font-size: 1em;
            opacity: 0.9;
            margin-bottom: 0;
        }

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

        #err_msg {
            margin-bottom: 20px;
            min-height: 20px;
        }

        .error-message {
            background: linear-gradient(135deg, #ff6b6b, #ff5252);
            color: white;
            padding: 12px 16px;
            border-radius: 10px;
            font-size: 0.9em;
            display: flex;
            align-items: center;
            gap: 8px;
            animation: shake 0.5s ease-in-out;
        }

        .success-message {
            background: linear-gradient(135deg, #51cf66, #40c057);
            color: white;
            padding: 12px 16px;
            border-radius: 10px;
            font-size: 0.9em;
            display: flex;
            align-items: center;
            gap: 8px;
            animation: fadeIn 0.5s ease-in-out;
        }

        @keyframes shake {
            0%, 100% { transform: translateX(0); }
            25% { transform: translateX(-5px); }
            75% { transform: translateX(5px); }
        }

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

        .form-control {
            margin-bottom: 25px;
            position: relative;
        }

        .form-control label {
            display: block;
            margin-bottom: 8px;
            color: #2d3748;
            font-weight: 600;
            font-size: 0.95em;
        }

        .input-group {
            position: relative;
            display: flex;
            align-items: center;
        }

        .form-control input {
            width: 100%;
            padding: 15px 20px;
            border: 2px solid #e2e8f0;
            border-radius: 12px;
            font-size: 1em;
            background: #f8f9fa;
            transition: all 0.3s ease;
            outline: none;
        }

        .form-control input:focus {
            border-color: #667eea;
            background: white;
            box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
            transform: translateY(-2px);
        }

        .form-control input:valid {
            border-color: #51cf66;
        }

        .form-control input::placeholder {
            color: #a0aec0;
        }

        .input-icon {
            position: absolute;
            right: 15px;
            color: #a0aec0;
            transition: color 0.3s ease;
            pointer-events: none;
        }

        .form-control input:focus + .input-icon {
            color: #667eea;
        }

        .id-check-group {
            display: flex;
            gap: 10px;
        }

        .id-check-group input {
            flex: 1;
        }

        #idcheck {
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            border: none;
            padding: 15px 20px;
            border-radius: 12px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            white-space: nowrap;
            font-size: 0.9em;
            min-width: 120px;
        }

        #idcheck:hover {
            transform: translateY(-2px);
            box-shadow: 0 8px 20px rgba(102, 126, 234, 0.3);
        }

        #idcheck:active {
            transform: translateY(0);
        }

        .submit-btn {
            width: 100%;
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            border: none;
            padding: 18px;
            border-radius: 12px;
            font-size: 1.1em;
            font-weight: 700;
            cursor: pointer;
            transition: all 0.3s ease;
            margin-top: 10px;
            position: relative;
            overflow: hidden;
        }

        .submit-btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
            transition: left 0.5s ease;
        }

        .submit-btn:hover::before {
            left: 100%;
        }

        .submit-btn:hover {
            transform: translateY(-3px);
            box-shadow: 0 12px 25px rgba(102, 126, 234, 0.4);
        }

        .submit-btn:active {
            transform: translateY(-1px);
        }

        .footer-links {
            text-align: center;
            margin-top: 30px;
            padding-top: 20px;
            border-top: 1px solid #e2e8f0;
        }

        .footer-links a {
            color: #667eea;
            text-decoration: none;
            font-weight: 600;
            transition: color 0.3s ease;
        }

        .footer-links a:hover {
            color: #764ba2;
            text-decoration: underline;
        }

        /* 반응형 디자인 */
        @media (max-width: 480px) {
            .container {
                margin: 10px;
                border-radius: 15px;
            }

            .header {
                padding: 30px 20px 20px;
            }

            .header h1 {
                font-size: 1.7em;
            }

            .form-container {
                padding: 30px 20px;
            }

            .id-check-group {
                flex-direction: column;
            }

            #idcheck {
                min-width: auto;
                width: 100%;
            }
        }

        /* 로딩 상태 */
        .loading {
            opacity: 0.7;
            pointer-events: none;
            position: relative;
        }

        .loading::after {
            content: '';
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            width: 20px;
            height: 20px;
            border: 2px solid transparent;
            border-top: 2px solid white;
            border-radius: 50%;
            animation: spin 1s linear infinite;
        }

        @keyframes spin {
            0% { transform: translate(-50%, -50%) rotate(0deg); }
            100% { transform: translate(-50%, -50%) rotate(360deg); }
        }

        /* 입력 필드 검증 상태 */
        .form-control.success input {
            border-color: #51cf66;
            background-color: #f0fff4;
        }

        .form-control.error input {
            border-color: #ff6b6b;
            background-color: #fff5f5;
        }

        .validation-message {
            font-size: 0.8em;
            margin-top: 5px;
            display: flex;
            align-items: center;
            gap: 5px;
        }

        .validation-message.success {
            color: #51cf66;
        }

        .validation-message.error {
            color: #ff6b6b;
        }