Too many ads
Thank you for your feedback! One ad plays between each full round of gameplay. Our advertising revenue allows us to provide ongoing support and development of the game, while keeping the game free for everyone. There is a Disable Ads add-on available in the store that removes video ads from the game. If you prefer, that option is there.
Thanks again for your feedback, which I will pass on to the team! We are always evaluating and tweaking frequency and length of ads.