    0%, 100% { opacity: 1; }
            50% { opacity: 0.5; }
        }
        
        /* Cell Prompt Area */
        .cell-prompt {
            width: 80px;
            padding: 8px;
            text-align: right;
            font-family: var(--font-mono);
            font-size: 12px;
            color: var(--text-color);
            opacity: 0.6;
            user-select: none;
        }
        
        .execution-count {
            display: inline-block;
        }
        
        .cell-running .exec