Tactics
The windmill
A rook and a bishop working together so that the rook swings out with discovered check, takes something, and swings back with check again. The defender can only answer the checks, so the rook collects a piece on every turn. Torre against Lasker in 1925 is the game everybody knows it from.
How to spot it
The ingredients are a bishop aiming at their king through a square your rook can stand on, and a rook that has a safe square to return to. Count the material before you start rather than during: a windmill ends when you run out of things to take, and the last swing has to leave you better than the first.
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.
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1. White to play Play it out →Answer
22.Bc1+ Nd2+ 23.Rxd2+ Qxd2 24.Bxd2
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2. White to play Play it out →Answer
11.Nxe5 Qxg5 12.Nf3+ Qe7 13.Rxe7+
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3. Black to play Play it out →Answer
18...Rxg2+ 19.Kh1 Rxe2+ 20.Kg1 Rg2+
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4. White to play Play it out →Answer
15.Nd6+ Kf8 16.Nxc8+ d6 17.Nxd6
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5. White to play Play it out →Answer
15.Nxe5+ axb5 16.Qxb5+ Bc6 17.Nxc6
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6. Black to play Play it out →Answer
37...Rd2 38.Nxd2 Rxg2+ 39.Kh1 Rxd2+ 40.Kg1 Rg2+
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7. White to play Play it out →Answer
24.Nh5+ Kg8 25.Rxf7 Kxf7 26.Qg7+ Ke8 27.Nf6+ Qxf6 28.Qxf6
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8. White to play Play it out →Answer
23.Nfg6+ Rxg6 24.Nxg6+ Kxh7 25.Ne7+ g6 26.Qxg6+ Kh8 27.Qh6#
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9. Black to play Play it out →Answer
35...Bh2+ 36.Kh1 Ng3+ 37.Bxg3 Bxg3+ 38.Kg1 Qh2#
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10. White to play Play it out →Answer
34.Rf1+ Bf4 35.Rxf4+ Kg5 36.Qe3 Qa1+ 37.Rf1+
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11. White to play Play it out →Answer
30.Ne4+ f6 31.Rh7+ Kf8 32.Bh6+ Kg8 33.Nxf6#
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12. White to play Play it out →Answer
33.Nf6+ Kf7 34.Qe6+ Kg6 35.Ne4+ Kh7 36.Ng5+ Kh8 37.Qe8#
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.