diff --git a/src/site/snake/brain-neat.ts b/src/site/snake/brain-neat.ts
index dff28ab..7db3b3e 100644
--- a/src/site/snake/brain-neat.ts
+++ b/src/site/snake/brain-neat.ts
@@ -382,11 +382,11 @@ export function chooseSurvivors(population: Population, fitness: Map<Genome, num
     return survivors;
 }
 
-interface BreedingConfig {
+interface MateChoiceConfig {
     asexual_rate: number;
     interspecies_rate: number;
 }
-export function chooseMate(genome: Genome, population: Population, config: BreedingConfig) {
+export function chooseMate(genome: Genome, population: Population, config: MateChoiceConfig) {
     const { asexual_rate, interspecies_rate } = config;
 
     if (Math.random() < asexual_rate) return genome;
@@ -421,12 +421,46 @@ export function chooseMate(genome: Genome, population: Population, config: Breed
 
 // TODO: function crossGenomes(mom: Genome, dad: Genome, fitness: Map<Genome, number>) { ... }
 interface CrossConfig {
-	reenable_rate: number;
+    reenable_rate: number;
 }
 export function crossGenomes(mom: Genome, dad: Genome, fitness: Map<Genome, number>, config: CrossConfig) {
-	const { reenable_rate } = config;
-	
-	const alignment = alignGenomes(mom, dad);
+    const { reenable_rate } = config;
+
+    const alignment = alignGenomes(mom, dad);
+
+    const crossed: Genome = [];
+
+    // matching
+    for (const { mom: momGene, dad: dadGene } of alignment.matching) {
+        const newWeight = Math.random() < 0.5 ? momGene.data.weight : dadGene.data.weight;
+        const wasDisabled = !momGene.data.enabled || !dadGene.data.enabled;
+        const newEnabled = !wasDisabled || Math.random() < reenable_rate;
+        const newGene = { ...momGene, data: { ...momGene.data, weight: newWeight, enabled: newEnabled } };
+        crossed.push(newGene);
+    }
+
+    // disjoint
+    const momFitness = fitness.get(mom)!;
+    const dadFitness = fitness.get(dad)!;
+    const mostFit = momFitness === dadFitness ? 'equal' : momFitness > dadFitness ? 'mom' : 'dad';
+    for (const { mom: momGene, dad: dadGene } of alignment.disjoint) {
+        if (momGene === null) crossed.push(dadGene as Gene);
+        else if (dadGene === null) crossed.push(momGene);
+        else if (mostFit === 'mom') crossed.push(momGene);
+        else if (mostFit === 'dad') crossed.push(dadGene);
+        // both are equally fit - select at random
+        else if (Math.random() < 0.5) crossed.push(momGene);
+        else crossed.push(dadGene);
+    }
+
+    // excess
+    for (const { mom: momGene, dad: dadGene } of alignment.excess) {
+        if (momGene === null) crossed.push(dadGene as Gene);
+        else if (dadGene === null) crossed.push(momGene as Gene);
+        else throw Error(`invalid excess alignment: alignment=${JSON.stringify(alignment)}`);
+    }
+
+    return crossed;
 }
 
 export function mutateAssign(gene: Gene, newWeight: number): Gene {