This year's Girls' Day was all about wallpapergroups. After an exciting talk on AI, our 11 girls started with the workshop on wallpapergroups. Each girl was able to choose her favorite pattern and check that it was indeed a wallpaper pattern, meaning that it could be moved congruently in two independent directions. We then discovered that the symmetries of wallpaper patterns are precisely the congruence mappings of the plane and that these form a group. Together we proved that there can only be four different rotations for wallpapergroups. This ultimately helped us show that there are only 17 wallpapergroups.

After a delicious lunch in the cafeteria, the participants learned more about groups at four different stations, identified wallpapergroups, found patterns in the Mathematikon, and painted patterns themselves.

Thus, an exciting first day as mathematicians at university came to a close.