The reactive inputs can then feed through to exercises, with both user and solution code reacting to the changes. This means leaners can be given parametrised questions, or interact with exercises in a more engaging way than just typing in lines of solution code. Learners can experiment with parameters live and see how things really change.

Things start to get really fun when you introduce ojs blocks into the mix. Interactive code blocks can interface with the ojs variables that also exist in the Quarto document. Existing variables can be included in the R environment, and R variables can be output as ojs variables. Since ojs handles its own reactive runtime and has a collection of standard reactive inputs, it's possible to create dynamic client-side experiences with very little glue code at all.

Adding `hint` and `solution` blocks creates an exercise, similar to the output of {learnr}. Hints and solutions can be revealed by the learner when required, making use of Quarto's excellent code presentation tools such as syntax and line highlighting, and code annotations. Since we're running webR under the hood, user submitted solutions can be graded using either grading algorithms written in R, or using the {gradethis} R package to compare learner submitted code to the solution block.

With this new extension, including a ```{webr} block inserts a runnable sandbox code editor into your Quarto document. The code outputs here are not just the R console's standard text-based output, but rich content generated through the {knitr} engine. The sandbox editor can be used to interactively output a wide range of items, with text, tables, plots, HTML widgets, and even errors rendered nicely into the page.

This release of webR powers a new project I've been working over the last few months, aiming to improve integration of WebAssembly engines like webR with Quarto and ojs, with particular focus on re-creating interactive exercises in the style of {learnr}. The basic idea is to use the reactivity provided by ojs as the backend for interactive client-side code blocks, powered by WebAssembly and using JavaScript for rich and responsive output.