Here is the official explanation of what the Activity is, which can be found on the same page where submissions should be uploaded:
Inventions for the future world, by the future of the world! For this Kid Inventors’ Day, we want to see what inventions you can come up with that could help save the planet, using LEGO bricks. The more creative, the better!
This is part of a series on LEGO Ideas that gives little tasks for builders to get involved with – there are no prizes, they are just a way to get involved with building something quick for fun. Each challenge is intended to be something quick and fun, unlike the more in-depth building required for a competition or product idea.
The deadline for this Activity is January 7 at 10.00am CEST.
The last LEGO Activity asked fans to build a plane.