ngthLabel);
        gateLengthContainer.appendChild(gateLengthSlider);
        controlsColumn.appendChild(gateLengthContainer);

        // Preview column
        const previewColumn = document.createElement('div');
        previewColumn.className = 'preview-column';
        
        const previewTitle = document.createElement('div');
        previewTitle.textContent = 'Preview';
        previewColumn.appendChild(previewTitle);

        const pianoRoll = document.createElement('div');
        pianoRoll.id =