kCTF is a Kubernetes-based infrastructure for CTF competitions.
If you want to quickly get started, follow the local testing walkthrough, this will show you how to build and test challenges locally.
If you want to read more about how kCTF works, take a look at kCTF in 8 minutes: A quick 8 minutes summary of what is kCTF and how it interacts with Kubernetes.
Once you have everything up and running, you can try deploying to Google Cloud. Follow the Google Cloud walkthrough.
You can also find a troubleshooting playbook (for fixing broken challenges), and a guide for setting up DNS for the CTF.
In the samples directory you can find a couple example web challenges. One of them is a challenge that acts as an XSS bot, and the other is a challenge that acts as a vulnerable PHP application with support for sessions and file uploads.