Since it seems like some websites still link here: This release is super outdated. Please install the latest release following the installation instructions here instead!
This is temporary release reflecting the development state of the add-on from a few months back. It is meant as an interim solution until v0.7.0 – the first official 2.1 release – becomes stable.
In order to install it you will have to move the review_heatmap folder into Anki's addons21 folder.
Please note that this is alpha-quality software. You should only use it if you know what you are doing. As this is an obsolete version of the add-on, I will not be able to address any issues that you might encounter, nor will I be able to provide any support.
v0.7.0, which packs a complete overhaul of the add-on and stable 2.1 support, will be ready soon. So my advice would be to just wait until then.