I've somehow managed to build a playable game already and have just tested uploading it to make sure the Web build plays on itch.io correctly.
It's pretty basic and only has three small levels. I could add loads more functionality to it, but I'm off on holiday tomorrow so stuck for time. I'm happy with what I managed to get done though, especially as this time I tried my hand at drawing the assets myself instead of searching the web for free ones.