Tactics
The discovered check
A discovered attack where the piece behind gives check. Because the check must be answered, the piece that stepped aside can do anything: capture something defended, land where it is attacked twice, walk into the middle of the board. For one move it is untouchable.
How to spot it
Any of your pieces sitting between one of your sliders and their king is a discovered check waiting to be fired. The question is never whether to fire it but where to send the front piece, so list the enemy pieces that are currently defended and ask which of them you would like to take for free.
The positions
Easiest first. Every one is from a real game, and the rating under each board is what it costs the players who have tried it on lichess.
-
1. Black to play Play it out →Answer
20...Bxd4+ 21.Kh1 Rg1#
-
2. White to play Play it out →Answer
30.Nh6+ Kh8 31.Qg8#
-
3. White to play Play it out →Answer
20.cxb5+ Qf7 21.Qxf7+ Kxf7 22.bxc6
-
4. Black to play Play it out →Answer
26...Nh3+ 27.Kf1 Qf2#
-
5. Black to play Play it out →Answer
36...Bxg2+ 37.Kxg2 h1=Q#
-
6. White to play Play it out →Answer
23.Bc1+ Kg7 24.Bxb2
-
7. White to play Play it out →Answer
14.Nf6+ Kh6 15.Qh5#
-
8. Black to play Play it out →Answer
17...Bxc5+ 18.d4 exd3+ 19.Be3 Bxe3#
-
9. White to play Play it out →Answer
35.Qxg8+ Kxg8 36.Nxf6+ Kh8 37.Rg8#
-
10. Black to play Play it out →Answer
21...Qxh2+ 22.Kxh2 Nf3+ 23.Kh3 Rh4#
-
11. White to play Play it out →Answer
31.Rc8+ Nf8 32.Rxf8+ Kxf8 33.d7+ Kg8 34.d8=Q#
-
12. White to play Play it out →Answer
32.Qg7+ Kxg7 33.Nxf5+ Kg8 34.Rxd8#
Reading about a pattern is the easy half. Motify finds the positions where you missed one, by running your own lichess and Chess.com games through Stockfish, and puts each of them behind two or three puzzles on the same idea so you meet it having just found it three times. See how Motify works.
Positions from the lichess puzzle database, released under CC0.