CryptICS is a project that tries to show different cryptographic principles and lets you practice different calculations surrounding cryptography. A more or less up to date version of the tool is available at cryptics.dschenker.ch.
For more information about the Tool, consult the project wiki.
The tool is written with a Python / FastAPI backend and a Svelte frontend. Both languages should be fairly easy to pick up if you have any experience in (object oriented) programming and web development respectively. The tool is based on a modular architecture, meaning you shouldn't have to understand or edit any (or only very little) existing code, which should let you focus on developing the functionality you are working on.
To get started, check out the in-depth developer documentation, which shows you how to set up the tool for developing, discusses the modular architecture, and has examples/templates for new modules as well as common patterns and reusable components.
Current work is tracked in Issues, if you want to contribute, create a new issue or grab an existing one.
If you encounter a bug, spot a mistake, or have a suggestion for an enhancment, open an Issue (preferred) or get in touch directly through the email address linked in the CryptICS profile or on the website.