Go inside the code and add a new costume using the Teslation Template and when your done duplicate your costume (Important Note: make sure your duplicated costume is directly underneath your original one) and then mirror it upside down (Important Note: use the Square Template costume to invert it and make sure the square is in the center so that the longest line in the triangle is flat against the x axis) and then go into the code, before the Draw Teslation block it switches the costume, switch the costume to YOUR FIRST teslation triangle and then it should work
