By length
Very long puzzles
Four moves or more — deep calculation and stamina.
What is the very long puzzles?
A very long puzzle takes four moves or more to finish. These are the deep ones: long forcing sequences, multiple defences to refute, and often a quiet move buried in the middle.
Why the very long puzzles matters
Long puzzles train calculation stamina — the ability to hold a position in your head and follow it accurately move after move. That endurance is what keeps you from cracking in complicated middlegames.
How to use it to win
Be patient and systematic: pick the forcing candidate, calculate it fully, and only then try the next. Keep the board sharp in your mind's eye and recheck the critical defence before you trust the line.
Try an example puzzle
A real very long puzzles puzzle from the app. Black to move — find the idea, then reveal the line.
5 
Show solution
1. ... Rxf5+ 2. Kxf5 a4 3. Ke4 a3 4. Kd3 a2
Drill the very long puzzles on thousands of real puzzles, matched to your rating.