` : `rgb(150, 150, 150)`
              ctx.font = "18px monospace";
              ctx.fillText(2, dx*binIndex - 6, 20);
              ctx.font = "12px monospace";
              ctx.fillText(i, dx*binIndex + 4, 11);
            });

            // draw latest response bar chart
            ctx.fillStyle =  `rgb(0, 200, 0)`;
            for (let i = 0; i < bufferLength; i++) {
              let scale = 0.8 * height / 256;
              let y = buffer[i]*scale;
              ctx.fillRect(i*dx, height - y, Math