diff --git a/src/common.ts b/src/common.ts
index dc3acf5..947e4d7 100644
--- a/src/common.ts
+++ b/src/common.ts
@@ -120,6 +120,8 @@ export const CardStringSuits: CardStringSuit[] = [
 	CardStringSuit.Choice
 ]
 
+export type ShuffleFunction = (cards: CardString[]) => CardString[]
+
 export { MoveTag } from "./MoveTag"
 export { Role } from "./Role"
 export { StatusCode } from "./StatusCode"
diff --git a/src/doCombat.ts b/src/doCombat.ts
index 0a22f1c..2950f99 100644
--- a/src/doCombat.ts
+++ b/src/doCombat.ts
@@ -1,5 +1,6 @@
-import { shuffle } from "@samual/lib/shuffle"
-import type { CardString, CardStringSuit, CardStringFace, Lane, State } from "./common"
+import type { LaxPartial } from "@samual/lib"
+import { shuffle as defaultShuffleFunction } from "@samual/lib/shuffle"
+import type { CardString, CardStringFace, CardStringSuit, Lane, ShuffleFunction, State } from "./common"
 import { CardStringFaceModifier, Role, StatusCode } from "./common"
 
 export type CombatData = {
@@ -20,7 +21,11 @@ export type CombatData = {
 
 export const PowersOfTwo = [ 2, 4, 8, 16, 32, 64, 128, 256 ]
 
-export function doCombat(state: State, lane: Lane): { status: StatusCode.Okay | StatusCode.AttackerWin } & CombatData {
+export function doCombat(
+	state: State,
+	lane: Lane,
+	{ shuffleFunction: shuffle = defaultShuffleFunction }: LaxPartial<{ shuffleFunction: ShuffleFunction }> = {}
+): { status: StatusCode.Okay | StatusCode.AttackerWin } & CombatData {
 	const roleTurn: Role = (state.turn % 2) + 1
 	const laneDeck = state.laneDecks[lane]
 	const laneDiscardPile = state.laneDiscardPiles[lane]
@@ -129,7 +134,7 @@ export function doCombat(state: State, lane: Lane): { status: StatusCode.Okay |
 	const attackerBouncesDiscarded: `?${CardStringSuit}`[] = []
 
 	if (
-		attackerBounceIndexes.length || defenderBounceIndexes.length || (!attackerAttackPower && !defenderAttackPower)
+		attackerBounceIndexes.length || defenderBounceIndexes.length || !(attackerAttackPower || defenderAttackPower)
 	) {
 		for (const index of defenderBounceIndexes.reverse()) {
 			const bounceDiscarded = defenderStack.splice(index, 1)[0]!
diff --git a/src/doMove.ts b/src/doMove.ts
index 5e6d2b4..1c1cce9 100644
--- a/src/doMove.ts
+++ b/src/doMove.ts
@@ -1,3 +1,6 @@
+import type { LaxPartial } from "@samual/lib"
+import type { CardString, Lane, Move, ShuffleFunction, State } from "./common"
+import { AttackerDeck, MoveTag, StatusCode } from "./common"
 import type { CombatData } from "./doCombat"
 import { doMoveCombat } from "./doMoveCombat"
 import { doMoveDiscard } from "./doMoveDiscard"
@@ -5,10 +8,8 @@ import { doMoveDraw } from "./doMoveDraw"
 import { doMovePass } from "./doMovePass"
 import { doMovePlay } from "./doMovePlay"
 import { doMovePlayFaceUp } from "./doMovePlayFaceUp"
-import type { CardString, Lane, Move, State } from "./common"
-import { AttackerDeck, MoveTag, StatusCode } from "./common"
 
-export function doMove(state: State, move: Move): {
+export function doMove(state: State, move: Move, options?: LaxPartial<{ shuffleFunction: ShuffleFunction }>): {
 	status: StatusCode.Okay | StatusCode.AttackerWin | StatusCode.DefenderWin
 	binlog: string[]
 } | { status: Exclude<StatusCode, StatusCode.Okay | StatusCode.AttackerWin | StatusCode.DefenderWin> } {
@@ -18,7 +19,7 @@ export function doMove(state: State, move: Move): {
 	switch (move.tag) {
 		case MoveTag.Draw: {
 			const deckIsEmpty = !(move.deck == AttackerDeck ? state.attackerDeck : state.laneDecks[move.deck]).length
-			const result = doMoveDraw(state, move.deck)
+			const result = doMoveDraw(state, move.deck, options)
 			const deck = move.deck == AttackerDeck ? `a` : move.deck
 
 			if (result.status == StatusCode.AttackerWin) {
@@ -63,7 +64,7 @@ export function doMove(state: State, move: Move): {
 		}
 
 		case MoveTag.PlayFaceUp: {
-			const result = doMovePlayFaceUp(state, move.card, move.lane)
+			const result = doMovePlayFaceUp(state, move.card, move.lane, options)
 
 			if (result.status == StatusCode.Okay || result.status == StatusCode.AttackerWin || result.status == StatusCode.DefenderWin) {
 				const binlog = [
@@ -84,7 +85,7 @@ export function doMove(state: State, move: Move): {
 		}
 
 		case MoveTag.Combat: {
-			const result = doMoveCombat(state, move.lane)
+			const result = doMoveCombat(state, move.lane, options)
 
 			if (result.status == StatusCode.Okay || result.status == StatusCode.DefenderWin || result.status == StatusCode.AttackerWin) {
 				const binlog = [
@@ -104,7 +105,7 @@ export function doMove(state: State, move: Move): {
 		}
 
 		case MoveTag.Discard: {
-			const result = doMoveDiscard(state, move.card, move.discardPile)
+			const result = doMoveDiscard(state, move.card, move.discardPile, options)
 
 			if (result.status == StatusCode.Okay || result.status == StatusCode.DefenderWin) {
 				const discardPile = move.discardPile == AttackerDeck ? `a` : move.discardPile
diff --git a/src/doMoveCombat.ts b/src/doMoveCombat.ts
index 9ceb75d..cd0245c 100644
--- a/src/doMoveCombat.ts
+++ b/src/doMoveCombat.ts
@@ -1,9 +1,10 @@
+import type { LaxPartial } from "@samual/lib"
+import type { Lane, ShuffleFunction, State } from "./common"
+import { Role, StatusCode } from "./common"
 import type { CombatData } from "./doCombat"
 import { doCombat } from "./doCombat"
-import type { Lane, State } from "./common"
-import { Role, StatusCode } from "./common"
 
-export function doMoveCombat(state: State, lane: Lane): (
+export function doMoveCombat(state: State, lane: Lane, options?: LaxPartial<{ shuffleFunction: ShuffleFunction }>): (
 	{ status: StatusCode.Okay | StatusCode.DefenderWin | StatusCode.AttackerWin } & CombatData
 ) | {
 	status:
@@ -22,7 +23,7 @@ export function doMoveCombat(state: State, lane: Lane): (
 	if (!state.attackerStacks[lane].length)
 		return { status: StatusCode.AttackerInitiatedCombatWithEmptyStack }
 
-	const combatResult = doCombat(state, lane)
+	const combatResult = doCombat(state, lane, options)
 
 	if (combatResult.status == StatusCode.AttackerWin)
 		return combatResult
diff --git a/src/doMoveDiscard.ts b/src/doMoveDiscard.ts
index 60ae71c..1ba8a0c 100644
--- a/src/doMoveDiscard.ts
+++ b/src/doMoveDiscard.ts
@@ -1,8 +1,14 @@
-import { shuffle } from "@samual/lib/shuffle"
-import type { CardString, CardStringFace, Lane, State } from "./common"
+import type { LaxPartial } from "@samual/lib"
+import { shuffle as defaultShuffleFunction } from "@samual/lib/shuffle"
+import type { CardString, CardStringFace, Lane, ShuffleFunction, State } from "./common"
 import { AttackerDiscardPile, Role, StatusCode } from "./common"
 
-export function doMoveDiscard(state: State, card: CardString | CardStringFace, discardPile: Lane | AttackerDiscardPile): {
+export function doMoveDiscard(
+	state: State,
+	card: CardString | CardStringFace,
+	discardPile: Lane | AttackerDiscardPile,
+	{ shuffleFunction: shuffle = defaultShuffleFunction }: LaxPartial<{ shuffleFunction: ShuffleFunction }> = {}
+): {
 	status: StatusCode.Okay | StatusCode.DefenderWin
 	cardDiscarded: CardString
 	cardsDrawn: [ CardString, CardString ] | undefined
diff --git a/src/doMoveDraw.ts b/src/doMoveDraw.ts
index 1ec12cc..4c4519f 100644
--- a/src/doMoveDraw.ts
+++ b/src/doMoveDraw.ts
@@ -1,8 +1,13 @@
-import { shuffle } from "@samual/lib/shuffle"
-import type { CardString, Lane, State } from "./common"
+import type { LaxPartial } from "@samual/lib"
+import { shuffle as defaultShuffleFunction } from "@samual/lib/shuffle"
+import type { CardString, Lane, ShuffleFunction, State } from "./common"
 import { AttackerDeck, AttackerDiscardPile, Role, StatusCode } from "./common"
 
-export function doMoveDraw(state: State, deckToDrawFrom: Lane | AttackerDeck): {
+export function doMoveDraw(
+	state: State,
+	deckToDrawFrom: Lane | AttackerDeck,
+	{ shuffleFunction: shuffle = defaultShuffleFunction }: LaxPartial<{ shuffleFunction: ShuffleFunction }> = {}
+): {
 	status: StatusCode.Okay | StatusCode.DefenderWin
 	cardDrawn: CardString
 } | {
diff --git a/src/doMovePlayFaceUp.ts b/src/doMovePlayFaceUp.ts
index 1ceffb5..03a5cf3 100644
--- a/src/doMovePlayFaceUp.ts
+++ b/src/doMovePlayFaceUp.ts
@@ -1,10 +1,16 @@
+import { LaxPartial } from "@samual/lib"
 import { assert } from "@samual/lib/assert"
+import type { CardString, CardStringFace, Lane, ShuffleFunction, State } from "./common"
+import { CardStringFaceModifier, Role, StatusCode } from "./common"
 import type { CombatData } from "./doCombat"
 import { doCombat } from "./doCombat"
-import type { CardString, CardStringFace, Lane, State } from "./common"
-import { CardStringFaceModifier, Role, StatusCode } from "./common"
 
-export function doMovePlayFaceUp(state: State, card: CardString | CardStringFace, lane: Lane): {
+export function doMovePlayFaceUp(
+	state: State,
+	card: CardString | CardStringFace,
+	lane: Lane,
+	options?: LaxPartial<{ shuffleFunction: ShuffleFunction }>
+): {
 	status: StatusCode.Okay | StatusCode.DefenderWin | StatusCode.AttackerWin
 	cardPlayed: CardString
 	combat: CombatData | undefined
@@ -43,7 +49,7 @@ export function doMovePlayFaceUp(state: State, card: CardString | CardStringFace
 
 			let status
 
-			({ status, ...combat } = doCombat(state, lane))
+			({ status, ...combat } = doCombat(state, lane, options))
 
 			if (status == StatusCode.AttackerWin)
 				return { status, cardPlayed, combat }
@@ -71,7 +77,7 @@ export function doMovePlayFaceUp(state: State, card: CardString | CardStringFace
 
 			let status
 
-			({ status, ...combat } = doCombat(state, lane))
+			({ status, ...combat } = doCombat(state, lane, options))
 
 			if (status == StatusCode.AttackerWin)
 				return { status, cardPlayed, combat }
@@ -81,7 +87,7 @@ export function doMovePlayFaceUp(state: State, card: CardString | CardStringFace
 
 			let status
 
-			({ status, ...combat } = doCombat(state, lane))
+			({ status, ...combat } = doCombat(state, lane, options))
 			assert(status != StatusCode.AttackerWin, `attacker won when playing a face up bounce`)
 		} else
 			return { status: StatusCode.PlayedCardFacedWrongWay }
diff --git a/src/simulateGame.ts b/src/simulateGame.ts
index f6b9a52..c811782 100644
--- a/src/simulateGame.ts
+++ b/src/simulateGame.ts
@@ -4,7 +4,7 @@ import type { BinmatArgs } from "./generateArgs"
 import { generateArgsForAttacker, generateArgsForDefender } from "./generateArgs"
 import { makeState } from "./makeState"
 import { parseMove } from "./parseMove"
-import type { MoveString, State } from "./common"
+import type { MoveString, ShuffleFunction, State } from "./common"
 import { MoveTag, Role, StatusCode, StatusCodeMessages } from "./common"
 
 export type SimulateGameOptions = {
@@ -23,6 +23,8 @@ export type SimulateGameOptions = {
 
 	/** Intial state of binlog from attacker's last turn (should be odd numbered turn) @default [] */
 	attackerBinlog: string[]
+
+	shuffleFunction: ShuffleFunction
 }
 
 export type CLIContext = {
@@ -56,7 +58,8 @@ export function simulateGame(
 		onMove,
 		state = makeState(),
 		defenderBinlog = [],
-		attackerBinlog = []
+		attackerBinlog = [],
+		shuffleFunction
 	}: LaxPartial<SimulateGameOptions> = {}
 ): Role {
 	let endTime: number
@@ -157,7 +160,7 @@ export function simulateGame(
 			throw error
 		}
 
-		const result = doMove(state, move)
+		const result = doMove(state, move, { shuffleFunction })
 
 		switch (result.status) {
 			case StatusCode.Okay: break
@@ -187,7 +190,7 @@ export function simulateGame(
 	}
 
 	function doDefaultMove() {
-		const result = doMove(state, { tag: MoveTag.Pass })
+		const result = doMove(state, { tag: MoveTag.Pass }, { shuffleFunction })
 
 		switch (result.status) {
 			case StatusCode.Okay: break