28th Jan 2002 Here is a way of constructing the glider gun in 744 moves. I started by finding a more efficient way of forming a blinker (21 moves) which boards a glider instead of forming a loaf. I also discovered a way to form a block and board a glider in only 17 moves! These routines are clear in the following construction of the glider gun. Start with the Y centered at (36,25). SS< Y to loaf U/LRUSSS>SS>SS>SS>SS>SS>SS Reposition glider >R\< Glider to loaf U>U\>/ULDDULSR/>R/SLULU\D< Fire glider to form ship Glider to loaf U>D<\DUR\DU\UR/L\ Loaf to rotated glider D Glider to loaf U>D<\RLUS>\/RDLU\/L/\ Form a blinker \SS\SS\SS\SS\SS\SS\SSD /LRUSSS>SS>SS>SS>SS>SS>SS Reposition glider >R\> Glider to loaf U>DU<U/ Form a block /SS/SS/SSL\SSR/SSL\SS Reposition glider \U>\ Glider to loaf R\LRDRDR>RSU\DL Fire glider to form ship >\S> Glider to loaf U>D<\DUR\DU\UR/L\ Loaf to rotated glider \SS\SS\SS\SS\SS\SSD Glider to loaf U>D<\RLUS>\/RDLU\/L/\ Form last blinker \SS Reposition glider \>S< Glider to loaf RU/ Loaf to rotated glider /SSL Reposition glider \>S/ Glider to loaf D/UD\\D>\ Form last block >SS>SS Reposition glider >D\> Glider to loaf L>R/\RLD\UDLSLUUUD/R>DUR> * Loaf to rotated glider >SS>SS>SSU/SS/SS/SS/SS/SS/SS Reposition glider /RL< Fire glider & light fuse /DUL/DU/UL\R/ Loaf to rotated glider D>SS>SS>SS>SS>SS>SS>SS>SS>SS >SS>SS>SS>SS>SS>SS>SS>SSU Race to the other side /ULSR/>R/SLULU\D< Fire last glider, which strikes 5 steps after the previous glider. At this point, the glider gun will evolve, and we used --- 744 moves. However, we are in the line of fire! So there is one more thing to do: U>D<\DUR\DU\UR/L\\SS\SS\SS... Get out of the way! A few comments: The biggest problem I encountered was parity. If the grid was painted in a checkerboard pattern, I would find that my glider is on the wrong color to put a given object at a given location. Luckily, whenever I rotated the glider, I could control the parity. But since I wanted to avoid the extra steps of a rotation, I had to form the still life in a different order than I first planed. The second biggest problem was interferrence from the objects that I already formed. The original plan was to have the gun fire away from the final position, but I had to flip the gun in order for the second blinker to be accessible. The * shows a longer routine for rotating a glider. However, this routine puts the glider closer to where I wanted to go, so it ended up saving me 4 steps. I discovered this savings by mistake -- there may be other similar places where several steps can be saved. Dr. Paulsen ----o00o---o00o---- Hang in there!