* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Microsoft YaHei', sans-serif;
        }
        
        body {
            background: linear-gradient(135deg, #1a2a6c 0%, #b21f1f 50%, #fdbb2d 100%);
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
        }
        
        .container {
            width: 100%;
            max-width: 800px;
            background-color: rgba(255, 255, 255, 0.95);
            border-radius: 15px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
            overflow: hidden;
        }
        
        header {
            background: linear-gradient(90deg, #4A00E0, #8E2DE2);
            color: white;
            padding: 20px;
            text-align: center;
        }
        
        h1 {
            font-size: 28px;
            margin-bottom: 10px;
        }
        
        .subtitle {
            font-size: 16px;
            opacity: 0.9;
        }
        
        .chat-area {
            padding: 20px;
            display: flex;
            flex-direction: column;
            gap: 20px;
        }
        
        .input-section, .output-section {
            display: flex;
            flex-direction: column;
            gap: 10px;
        }
        
        label {
            font-weight: bold;
            color: #333;
        }
        
        textarea {
            width: 100%;
            min-height: 100px;
            padding: 12px;
            border: 2px solid #ddd;
            border-radius: 8px;
            resize: vertical;
            font-size: 16px;
            transition: border-color 0.3s;
        }
        
        textarea:focus {
            border-color: #4A00E0;
            outline: none;
        }
        
        .buttons {
            display: flex;
            gap: 10px;
        }
        
        button {
            flex: 1;
            padding: 12px;
            border: none;
            border-radius: 8px;
            font-size: 16px;
            font-weight: bold;
            cursor: pointer;
            transition: all 0.3s;
        }
        
        #encryptBtn {
            background: linear-gradient(90deg, #4A00E0, #8E2DE2);
            color: white;
        }
        
        #decryptBtn {
            background: linear-gradient(90deg, #f46b45, #eea849);
            color: white;
        }
        
        #copyBtn {
            background: linear-gradient(90deg, #00b09b, #96c93d);
            color: white;
            max-width: 200px;
            margin-top: 10px;
            align-self: flex-end;
        }
        
        button:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
        }
        
        button:active {
            transform: translateY(0);
        }
        
        .history {
            margin-top: 20px;
            border-top: 1px solid #eee;
            padding-top: 20px;
        }
        
        .history h3 {
            margin-bottom: 10px;
            color: #333;
        }
        
        #historyList {
            list-style-type: none;
            max-height: 200px;
            overflow-y: auto;
            border: 1px solid #eee;
            border-radius: 8px;
            padding: 10px;
        }
        
        .history-item {
            padding: 8px;
            margin-bottom: 8px;
            background-color: #f9f9f9;
            border-radius: 5px;
            border-left: 4px solid #4A00E0;
        }
        
        .history-item.encrypted {
            border-left-color: #f46b45;
        }
        
        .char-mapping {
            margin-top: 15px;
            padding: 10px;
            background-color: #f0f8ff;
            border-radius: 8px;
            font-size: 14px;
            text-align: center;
        }
        
        .char-mapping h4 {
            margin-bottom: 5px;
            color: #333;
        }
        
        .example {
            margin-top: 15px;
            padding: 10px;
            background-color: #fff8e1;
            border-radius: 8px;
            font-size: 14px;
        }
        
        .example h4 {
            margin-bottom: 5px;
            color: #333;
        }
        
        footer {
            text-align: center;
            padding: 15px;
            background-color: #f5f5f5;
            color: #666;
            font-size: 14px;
        }
        
        .copy-notification {
            position: fixed;
            top: 20px;
            right: 20px;
            background-color: #4CAF50;
            color: white;
            padding: 15px 25px;
            border-radius: 5px;
            box-shadow: 0 3px 10px rgba(0,0,0,0.2);
            opacity: 0;
            transition: opacity 0.3s;
            z-index: 1000;
        }
        
        .copy-notification.show {
            opacity: 1;
        }
        
        @media (max-width: 600px) {
            .buttons {
                flex-direction: column;
            }
            
            h1 {
                font-size: 24px;
            }
            
            #copyBtn {
                max-width: 100%;
                align-self: stretch;
            }
        }