Misere combinatorial games.
A set of games $\mathcal{A}$ is integer-invertible if it contains every integer $n$ and $n + \overline{n} =_{\mathcal{A}} 0$.
This is [Davies, Miller, Milley (Definition 3.12 on p. 15)][davies:SumsPFreeForms:2025].
Instances
If $\mathcal{A}$ is integer-invertible then so is $\operatorname{pf}(\mathcal{A})$.
If $0 \in \mathcal{A}$ and $G =_{\mathcal{A}} H$ then $\operatorname{o}(G) = \operatorname{o}(H)$.
If $\mathcal{A}$ is integer-invertible, $G, H \in \mathcal{A}$, and $n \in \mathbb{Z}$ then $$ G + H =_{\mathcal{A}} (G + n) + (H - n). $$
If $\mathcal{A}$ is integer-invertible, $G, H \in \mathcal{A}$, and $n \in \mathbb{Z}$ then $$ \operatorname{o}(G + H) = \operatorname{o}((G + n) + (H - n)). $$
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{L}$ then if $\operatorname{n}(G) > \operatorname{l}(H)$ then $\operatorname{o}(G + H) = \mathscr{L}$.
This is (1) in [Davies, Miller, Milley (Lemma 3.13 on p. 16)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{L}$ and $\operatorname{o}(H) = \mathscr{N}$, then if $\operatorname{r}(G) < \operatorname{l}(H)$ then $\operatorname{o}(G + H) = \mathscr{N}$.
This is (2) in [Davies, Miller, Milley (Lemma 3.13 on p. 16)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \operatorname{o}(H) = \mathscr{N}$ then if $\operatorname{r}(G) > \operatorname{l}(H)$ or $\operatorname{l}(G) < \operatorname{r}(H)$ then $\operatorname{o}(G + H) \ge \mathscr{N}$.
This is [Davies, Miller, Milley (Lemma 3.14 on p. 16)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{L}$ and $\operatorname{l}(H) < \operatorname{n}(G)$, then $\operatorname{o}(G + H) = \mathscr{L}$.
This is (1) in [Davies, Miller, Milley (Lemma 3.15 on p. 17)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{L}$, $\operatorname{o}(H) = \mathscr{R}$ and $\operatorname{n}(G) > \operatorname{n}(H)$ or $\operatorname{r}(G) > \operatorname{l}(H)$, then $\operatorname{o}(G + H) \ge \mathscr{N}$.
This is (2) in [Davies, Miller, Milley (Lemma 3.15 on p. 17)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{R}$ then if $\operatorname{r}(H) < \operatorname{n}(G)$ then $\operatorname{o}(G + H) = \mathscr{R}$.
This is mirror of (1) in [Davies, Miller, Milley (Lemma 3.13 on p. 16)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{R}$ and $\operatorname{o}(H) = \mathscr{N}$, then if $\operatorname{l}(G) < \operatorname{r}(H)$ then $\operatorname{o}(G + H) = \mathscr{N}$.
This is mirror of (2) in [Davies, Miller, Milley (Lemma 3.13 on p. 16)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \operatorname{o}(H) = \mathscr{N}$ then if $\operatorname{r}(G) < \operatorname{l}(H)$ or $\operatorname{l}(G) > \operatorname{r}(H)$ then $\operatorname{o}(G + H) \le \mathscr{N}$.
This is mirror of [Davies, Miller, Milley (Lemma 3.14 on p. 16)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{R}$ and $\operatorname{r}(H) < \operatorname{n}(G)$, then $\operatorname{o}(G + H) = \mathscr{R}$.
This is mirror of (1) in [Davies, Miller, Milley (Lemma 3.15 on p. 17)][davies:SumsPFreeForms:2025].
If $\mathcal{A}$ is an outcome-stable and integer-invertible monoid, and $G, H \in \operatorname{pf}(\mathcal{A})$ with $\operatorname{o}(G) = \mathscr{R}$, $\operatorname{o}(H) = \mathscr{L}$ and $\operatorname{n}(G) < \operatorname{n}(H)$ or $\operatorname{r}(H) < \operatorname{l}(G)$, then $\operatorname{o}(G + H) \le \mathscr{N}$.
This is mirror of (2) in [Davies, Miller, Milley (Lemma 3.15 on p. 17)][davies:SumsPFreeForms:2025].