You may have seen this year's April Fools xkcd. If you haven't, here's how it works:
When you visit that link, it generates an id on the end of the URL. Bookmark that.
You get a bare 'garden' with a lamp floating in mid-air. You can position the lamp and change its colour and the width of the beam. You can add and remove lamps, but you can't have more than three at once.
If you wait, stuff grows where the lamps are shining. Blue lamps grow 'wet' things such as octopuses. Red lamps grow dry things such as cacti and tortoises. Yellow lamps, in the middle of the spectrum, grow various plants and animals and things. Most of the things never grow bigger once they're there, but the large trees generate a bare trunk first and then randomly add branches and leaves.
If you don't like a thing, you can select it and delete or press the X button to remove it. This includes individual leaves and branches of large trees.
You can share your link with people, and they will see it without being able to change it. If you clear your cookies, you won't be able to edit either.
Here's mine.