Natural 1♦

This opening shows 4+♦ and usually 5+♦. It gets more unbalanced as the strength increases.

StrengthDistribution
12–145+♦ or 4♦(441)
15–17UNBAL, 5+♦ or 4♦(441)
18–20UNBAL, 5+♦, 0–3♠, 0–3♥

Unlike Polish Club 2020, I use standard (i.e. non-inverted) minor raises along with mixed raises to maximize preemption. This method utilized the frequent 5th diamond in the 1♦ opening.

Note that 1♦-2♣ is sometimes a phony suit. It is the only way to bid a game-forcing hand with long diamonds and no side major suit.

1♦-12–20, 5+♦ or 4♦(441)
1♥F, 4+♥, usually 6+
1♠F, 4+♠, usually 6+
1NTNF, 6–10, 4+♣
2♣FG, 4+♣ or 4+♦
2♦NF, 6–10, 3+♦
2♥!P/C, 7–9, 4+♥, 5+♠
2♠!UNBAL INV, 4+♦ or 6+♣
2NTBAL INV, 10–11
3♣!CONST, 7–9, 4+♦
3♦PRE, 4–6, 4+♦
3♥!FG SPL, 0–1♥, 0–3♠, 4+♦
3♠!FG SPL, 0–1♠, 0–3♥, 4+♦
3NT12–15, 1–3♠, 1–3♥

P-1♦

Game forcing 2♣ becomes a natural invitation. Consequently, 2♠ is a limit raise because it no longer takes care of clubs.

P-1♦-12–20, 5+♦ or 4♦(441)
2♣INV, 5+♣, 0–3♠, 0–3♥
2♠!LIM, 3+♦