Puzzle description: This is a simple but mysterious puzzle with triangles: Five yellow pieces fill a square frame loosely. The task is to pack the additional red triangle into the frame.

If you can read German: Mehr Informationen gibt es in https://welt-der-geduldspiele.blogspot.com/search?q=3D-Druck

Puzzle difficulty: The puzzle is fun and solvable even for children. Moreover, the solution can be applied to more melting block puzzles having angles of 45 degrees.

Printing instructions: The STL file was generated using PuzzleCAD: https://www.thingiverse.com/thing:3198014, the PuzzleCAD file is included. Prints are easy with no supports. I printed the puzzle in PLA at 0.1 mm layer height.