nice but not hard
The Best and Most Difficult Chess Puzzles Ever

I don't know about most difficult ever, but this one's pretty hard. Construct a legal drawn position with White to move and no promoted pieces, such that at least the first 17 half-moves are "only" moves for both sides. (White has only one move to draw, then Black has only one move to draw, then White has only one move to draw, then Black has only one move to draw, etc.)
Why 17? To improve on the position I found that starts with 16 consecutive "only" half-moves.
Tiger-13 the creator mentioned that the black agreed to mirror the white moves. So he has to move the queen and thus can't move bishop
in puzzle 4 third move can be bf4 and when black plays bf5 then queen takes f5 queen takes f4 and qc8

The first composition is a classic by Friedrich Amelung in 1897, while the next three were by Sam Loyd, again in the 19th century. I'd like to know who the author of the study is.

This isn't actually that hard, but I thought it would be fun to submit it...
If 1....gxf3 then 2. Bf4 fxg3 3. Bxf3+ g2+ 4. Bxg2#

You want something difficult?
Solve this:
Add 10 black knights and all necessary white pieces to create a legal position in which white to move either stalemates or loses. (Yes, it can be done!)
can you submitte daily puzzles daily