Keep pixels crip when scaling up

[liautaud]

Hi, I just started playing around with the demo, it's really cool 🙏!

One thing I would suggest, though, is to add image-rendering: pixelated; or image-rendering: crisp-edges; (depending on the browser) to the <canvas> in the web app to avoid the blur that can be seen on the scaled-up versions right now.

[takahirox]

Thanks for the suggestion! Do you want to make a PR? I'm not good at CSS.