Zooming / dragging on PC touchscreen

I'm new to CalTopo - looking to switch over from Gaia after all the changes there. 

First impressions on desktop - it seems like I can't zoom in/out (with pinching) or drag the map around using the touchscreen. Am I missing something? This seems like a weird function not to have.  

Using Chrome on a Lenovo IdeaPad Flex 5. Touchscreen itself is fine (i.e. I can press the +/- buttons and it zooms, double tap to zoom works too).