## On the Subject of Flipping Triangles

No, you’re not upside down.

*Please see Appendix 1PP1NG for identifying modules in the Triangles family.*

This module will have 9 triangles on it. Each of them is either grey or off. To solve the module, press the valid triangle each time. Pressing a triangle will turn it off and change the next valid triangle. If no more valid triangles are present on the module after pressing a triangle, the module will solve. **Note that triangles turn off when pressed, regardless of validity.**

### Identifying the valid triangle

Start with 0. For each triangle in the order shown on the image in the top-right part of this page, double your number, and add 1 if it is grey, or 0 if it’s off. Finally repeatedly sum the number’s digits together to get a new number until it becomes a single digit. The valid triangle is the one in this position in reading order (with the topmost triangle being 1).