diff --git a/engine/battle/core.asm b/engine/battle/core.asm
index e229b421b..55b896293 100644
--- a/engine/battle/core.asm
+++ b/engine/battle/core.asm
@@ -1982,6 +1982,7 @@ GetTwoThirdsMaxHP:
 	ld [hDivisor], a
 	ld b, 2
 	call Divide
+GetTwoThirdsMaxHP_end:
 	ld a, [hQuotient + 2]
 	ld b, a
 	ld a, [hQuotient + 3]
@@ -1993,6 +1994,19 @@ GetTwoThirdsMaxHP:
 .ok
 	ret
 
+GetOneSixthMaxHP:
+	call GetMaxHP
+
+	ld a, b
+	ld [hDividend + 0], a
+	ld a, c
+	ld [hDividend + 1], a
+	ld a, 6
+	ld [hDivisor], a
+	ld b, 2
+	call Divide
+	jr GetTwoThirdsMaxHP_end
+
 GetMaxHP:
 ; output: bc, wHPBuffer1
 
@@ -4242,6 +4256,22 @@ BreakAttraction:
 	res SUBSTATUS_IN_LOVE, [hl]
 	ret
 
+GetSpikesDamage:
+	dec a
+	jr z, .one ; one spikes set
+	dec a
+	jr z, .two ; two spikes set
+; assume three spikes set
+.three
+	call GetQuarterMaxHP
+	ret
+.two
+	call GetOneSixthMaxHP
+	ret
+.one
+	call GetEighthMaxHP
+	ret
+
 SpikesDamage:
 	ld hl, wPlayerScreens
 	ld de, wBattleMonType
@@ -4254,7 +4284,9 @@ SpikesDamage:
 	ld bc, UpdateEnemyHUD
 .ok
 
-	bit SCREENS_SPIKES, [hl]
+	ld a, [hl]
+	and 3
+	; return if zero spikes set
 	ret z
 
 	; Flying-types aren't affected by Spikes.
@@ -4267,11 +4299,15 @@ SpikesDamage:
 	ret z
 
 	push bc
+	push hl
 
 	ld hl, BattleText_UserHurtBySpikes ; "hurt by SPIKES!"
 	call StdBattleTextbox
 
-	call GetEighthMaxHP
+	pop hl
+	ld a, [hl]
+	and 3
+	call GetSpikesDamage
 	call SubtractHPFromTarget
 
 	pop hl
diff --git a/engine/battle/move_effects/rapid_spin.asm b/engine/battle/move_effects/rapid_spin.asm
index beac7af45..d63ca9896 100644
--- a/engine/battle/move_effects/rapid_spin.asm
+++ b/engine/battle/move_effects/rapid_spin.asm
@@ -16,9 +16,12 @@ BattleCommand_ClearHazards:
 	ld hl, wEnemyScreens
 	ld de, wEnemyWrapCount
 .got_screens_wrap
-	bit SCREENS_SPIKES, [hl]
+	ld a, [hl]
+	and 3
 	jr z, .no_spikes
-	res SCREENS_SPIKES, [hl]
+	ld a, [hl]
+	and $fc ; Clear spike bits
+	ld [hl], a
 	ld hl, BlewSpikesText
 	push de
 	call StdBattleTextbox
diff --git a/engine/battle/move_effects/spikes.asm b/engine/battle/move_effects/spikes.asm
index 24683cc59..d25818f28 100644
--- a/engine/battle/move_effects/spikes.asm
+++ b/engine/battle/move_effects/spikes.asm
@@ -8,12 +8,21 @@ BattleCommand_Spikes:
 
 ; Fails if spikes are already down!
 
-	bit SCREENS_SPIKES, [hl]
-	jr nz, .failed
+	ld a, [hl]
+	and 3
+	cp 3
+	jr nc, .failed
 
 ; Nothing else stops it from working.
 
-	set SCREENS_SPIKES, [hl]
+	push bc
+	inc a
+	ld b, a
+	ld a, [hl]
+	and $fc
+	or b
+	ld [hl], a
+	pop bc
 
 	call AnimateCurrentMove