Ask HN: What's a *fun* technology to use for MVP's?

What do you all think a fun tech-stack/framework to learn and write an application with would be? Performance, productivity, etc all are secondary concerns, bonuses of course, but second to the joy of using the technology.

I know this is super subjective, just interested in hearing what everyone thinks would be fun and why. I've got an idea for a relatively simple side-project and this feels like a good time to experiment and have some fun with it. I don't intend to ever need to scale it or need it to be particularly robust - not to say scalability and robustness aren't nice-to-have's, just again that they are not my foremost concern,