Size limit and the libraries
https://js13kgames.com/webxr-src/three.module.js instead (it contains r107 and WebVR helper as well).
You can freely use A-Frame components if you fit them inside the package. Remember that some of them may try to download extra resources, which is not allowed, so you have to modify them for your use in the competition.
WebXR versus other categories
Given the specificity of this category, and that entries using the library for "free" have technological advantage over other entries, the WebXR category is treated as an entirely separate one. You can submit your game to any (or all) of the three classic categories (Desktop and/or Mobile and/or Server) OR to the WebXR category alone.
Submitting your entry
The standard submit form will soon be open. Remember to select the WebXR category as the only one from the available options. The A-Frame, Babylon.js, or Three.js libraries cannot be included in the zipped package, only linked to - the zip without it should be 13 kilobytes or less.
The judges in this category are here to focus on your entries. Every judge will try to vote for every entry submitted to the WebXR category, and provide constructive feedback - what was great and what could be improved.
This device is sponsored by Mozilla Mixed Reality team. Given the specificity of shipping hardware worldwide, and issues it may cause given various customs services around the world, this prize is not guaranteed. We will do our best to ship you the prize, but you might have to pay extra taxes or other costs of importing such device to your country.
If You have any questions about this category feel free to contact us via e-mail: firstname.lastname@example.org.
Other options include visiting our profiles on Twitter or Facebook, or joining our Slack channel.