st type = gl.UNSIGNED_SHORT
        const offset = 0
        gl.drawElements(gl.TRIANGLES, vertexCount, type, offset)
      }

      cubeRotation += deltaTime
    }

    function initShaderProgram(gl, vsSource, fsSource) {
      const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource)
      const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource)

      const shaderProgram = gl.createProgram()
      gl.attachShader(shaderProgram, vertexShader)
      gl.attachShader(shaderProgram, fragmentS