diff --git a/doc/notes.txt b/doc/notes.txt
index 0360145a..1233f811 100644
--- a/doc/notes.txt
+++ b/doc/notes.txt
@@ -96,6 +96,7 @@ TODO:
 - show .map file in listings?
 - open ROM from URL?
 - #include can't have comment immediately on line before
+- NES: breakpoint on illegal instruction
 
 
 WEB WORKER FORMAT
diff --git a/presets/nes/ex4.asm b/presets/nes/ex4.asm
new file mode 100644
index 00000000..eeebaad8
--- /dev/null
+++ b/presets/nes/ex4.asm
@@ -0,0 +1,128 @@
+
+	include "nesdefs.asm"
+
+;;;;; VARIABLES
+
+	seg.u RAM
+	org $0
+
+ScrollX	byte	; used during NMI
+ScrollY	byte	; used during NMI
+
+;;;;; NES CARTRIDGE HEADER
+
+	NES_HEADER 0,2,1,0 ; mapper 0, 2 PRGs, 1 CHR, horiz. mirror
+
+;;;;; START OF CODE
+
+Start:
+	NES_INIT		; set up stack pointer, turn off PPU
+        jsr WaitSync
+        jsr WaitSync
+        jsr ClearRAM
+        jsr WaitSync		;wait for VSYNC
+	jsr SetPalette		;set colors
+        jsr FillVRAM		;set PPU RAM
+        jsr WaitSync		;wait for VSYNC (and PPU warmup)
+        lda #0
+        sta PPU_ADDR
+        sta PPU_ADDR		;PPU addr = 0
+        sta PPU_SCROLL
+        sta PPU_SCROLL		;scroll = 0
+        lda #CTRL_NMI
+        sta PPU_CTRL	; enable NMI
+        lda #MASK_BG|MASK_SPR
+        sta PPU_MASK 	; enable rendering
+.endless
+	jmp .endless		;endless loop
+
+; fill video RAM
+FillVRAM: subroutine
+	txa
+	ldy #$20
+	sty PPU_ADDR
+	sta PPU_ADDR
+	ldy #$10
+.loop:
+	stx PPU_DATA
+	inx
+	bne .loop
+	dey
+	bne .loop
+        rts
+
+; set palette colors
+
+SetPalette: subroutine
+        ldy #$00
+	lda #$3f
+	sta PPU_ADDR
+	sty PPU_ADDR
+	ldx #32
+.loop:
+	lda Palette,y
+	sta PPU_DATA
+        iny
+	dex
+	bne .loop
+        rts
+
+
+;;;;; COMMON SUBROUTINES
+
+	include "nesppu.asm"
+
+;;;;; INTERRUPT HANDLERS
+
+NMIHandler:
+	SAVE_REGS
+; update scroll position (must be done after VRAM updates)
+	jsr ReadJoypad
+        pha
+        and #$03
+        tay
+        lda ScrollDirTab,y
+        clc
+        adc ScrollX
+        sta ScrollX
+        sta PPU_SCROLL
+        pla
+        lsr
+        lsr
+        and #$03
+        tay
+        lda ScrollDirTab,y
+        clc
+        adc ScrollY
+        sta ScrollY
+        sta PPU_SCROLL
+; reload registers
+        RESTORE_REGS
+	rti
+
+; Scroll direction lookup table
+ScrollDirTab:
+	hex 00 01 ff 00
+ 
+;;;;; CONSTANT DATA
+
+	align $100
+Palette:
+	hex 1f		;background
+	hex 09090000	;bg0
+        hex 09090c00	;bg1
+        hex 09091c00	;bg2
+        hex 09092c00	;bg3
+        hex 14243400	;sp0
+        hex 15253500	;sp1
+        hex 16263600	;sp2
+        hex 17273700	;sp3
+
+;;;;; CPU VECTORS
+
+	NES_VECTORS
+
+;;;;; TILE SETS
+
+	org $10000
+        incbin "jroatch.chr"
diff --git a/src/platform/nes.ts b/src/platform/nes.ts
index 92a948d5..6c6c1d56 100644
--- a/src/platform/nes.ts
+++ b/src/platform/nes.ts
@@ -13,6 +13,7 @@ const JSNES_PRESETS = [
   {id:'ex1.asm', name:'Hello World (ASM)'},
   {id:'ex2.asm', name:'Scrolling Demo (ASM)'},
   {id:'ex3.asm', name:'Sprite Demo (ASM)'},
+  {id:'ex4.asm', name:'Controller Demo (ASM)'},
   {id:'neslib1.c', name:'Text'},
   {id:'neslib2.c', name:'Sprites'},
   {id:'neslib3.c', name:'Cursor'},