diff --git a/README.md b/README.md
index 243b43f..ba7d255 100644
--- a/README.md
+++ b/README.md
@@ -31,15 +31,13 @@ A [stack-based VM](https://wiki.xxiivv.com/site/uxn.html), written in ANSI C.
 ( hello world )
 
 ;iterator
-:dev1r FFF0
-:dev1w FFF1
 
 |0100 @RESET
 
-@word1 "hello_word ( len: 0x0b )
+@word1 "hello_world ( len: 0x0b )
 
 @loop
-	,dev1w STR ( write to stdout )
+	,00 IOW ( write to device#0 )
 	,incr JSR ( increment itr )
 	,word1 ,strlen JSR ( get strlen )
 	NEQ ,loop ROT JSR? ( loop != strlen )
@@ -64,25 +62,11 @@ BRK
 
 ## TODOs
 
-### Assembler
-
-- Implement shorthand operators
-- Signed operations
-
-### CPU
-
-- Signed operations
-- Catch overflow/underflow
-- A Three-Way Decision Routine(http://www.6502.org/tutorials/compare_instructions.html)
-- Draw pixel to screen
-- Redo overflow/underflow mappping
-- Detect mouse click
-- SDL Layer Emulator
-- Build PPU
-
-### Devices
-
-- Devices each have an input byte, an output byte and two request bytes.
+- Implement signed flag to operators.
+- On-screen debugger.
+- 16b mode for str/ldr
+- Auto-advance ldr?
+- Getting rid of IOR/IOW would be nice..
 
 ## Refs
 
diff --git a/emulator.c b/emulator.c
index a839729..e3a6078 100644
--- a/emulator.c
+++ b/emulator.c
@@ -59,7 +59,7 @@ void
 putpixel(Uint32 *dst, int x, int y, int color)
 {
 	if(x >= 0 && x < WIDTH - 8 && y >= 0 && y < HEIGHT - 8)
-		dst[(y + PAD * 8) * WIDTH + (x + PAD * 8)] = theme[color];
+		dst[y * WIDTH + x] = theme[color];
 }
 
 void
@@ -145,14 +145,18 @@ echof(Uxn *c)
 void
 domouse(SDL_Event *event)
 {
-	devmouse->mem[0] = event->motion.x / ZOOM - PAD * 8;
-	devmouse->mem[1] = event->motion.y / ZOOM - PAD * 8;
+	int x = event->motion.x / ZOOM;
+	int y = event->motion.y / ZOOM;
+	devmouse->mem[0] = (x >> 8) & 0xff;
+	devmouse->mem[1] = x & 0xff;
+	devmouse->mem[2] = (y >> 8) & 0xff;
+	devmouse->mem[3] = y & 0xff;
 	switch(event->type) {
 	case SDL_MOUSEBUTTONUP:
-		devmouse->mem[2] = 0;
+		devmouse->mem[4] = 0;
 		break;
 	case SDL_MOUSEBUTTONDOWN:
-		devmouse->mem[2] = event->button.button == SDL_BUTTON_LEFT;
+		devmouse->mem[4] = event->button.button == SDL_BUTTON_LEFT;
 	}
 }
 
@@ -186,9 +190,7 @@ consolew(Device *d, Uint8 b)
 Uint8
 screenr(Device *d, Uint8 b)
 {
-	(void)b;
-	(void)d;
-	return 0;
+	return d->mem[b];
 }
 
 Uint8
@@ -197,8 +199,8 @@ screenw(Device *d, Uint8 b)
 	d->mem[d->len++] = b;
 	if(d->len > 5) {
 		putpixel(pixels,
-			(d->mem[0] << 8) + d->mem[1],
 			(d->mem[2] << 8) + d->mem[3],
+			(d->mem[0] << 8) + d->mem[1],
 			d->mem[4]);
 		if(d->mem[5])
 			redraw(pixels);
@@ -244,6 +246,11 @@ start(Uxn *u)
 {
 	int ticknext = 0;
 	evaluxn(u, u->vreset);
+
+	echos(&u->wst, 0x40, "stack");
+	echom(&u->ram, 0x40, "ram");
+	echof(u);
+
 	while(1) {
 		int tick = SDL_GetTicks();
 		SDL_Event event;
@@ -286,6 +293,11 @@ main(int argc, char **argv)
 	devmouse = portuxn(&u, "mouse", mouser, mousew);
 	devkey = portuxn(&u, "key", keyr, keyw);
 
+	devscreen->mem[0] = (WIDTH >> 8) & 0xff;
+	devscreen->mem[1] = WIDTH & 0xff;
+	devscreen->mem[2] = (HEIGHT >> 8) & 0xff;
+	devscreen->mem[3] = HEIGHT & 0xff;
+
 	start(&u);
 
 	echos(&u.wst, 0x40, "stack");
diff --git a/examples/mouse.usm b/examples/mouse.usm
index 3b61950..bf98259 100644
--- a/examples/mouse.usm
+++ b/examples/mouse.usm
@@ -1,46 +1,40 @@
-( draw pixel )
+( mouse )
 
-|0100 @RESET
+:dev/r fff8 ( std read port )
+:dev/w fff9 ( std write port )
+
+|0100 @RESET 
 	
-	( draw 3 pixels )
-	,00 ,01 ,0000 ,0000 ,putpixel JSR
-	,00 ,02 ,0001 ,0001 ,putpixel JSR
-	,01 ,03 ,0002 ,0002 ,putpixel JSR
+	,02 ,dev/r STR ( set dev/read mouse#02 )
+	,01 ,dev/w STR ( set dev/write screen#01 )
 
 BRK
 
-|c000 @FRAME 
-	
+|c000 @FRAME
+
 	( get mouse button, or break )
-	,02 ,02 IOR
+	,04 IOR
 	,01 NEQ
 	BRK?
-
-	( print A to console on click )
-	,02 ,02 IOR
-	,41 ADD 
-	,putbyte JSR
-
+		
 	( paint a white pixel )
 	,01 ,01 
 	,getmouse JSR
 	,putpixel JSR
-BRK 
+
+BRK
+
+@getmouse
+	,00 IOR^ ( get mouse x )
+	,02 IOR^ ( get mouse y )
+	RTS
 
 @putpixel 
-	SWP ,01 IOW ,01 IOW ( y )
-	SWP ,01 IOW ,01 IOW ( x )
-	,01 IOW ( color )
-	,01 IOW ( redraw )
+	IOW^ ( y short )
+	IOW^ ( x short )
+	IOW ( color byte )
+	IOW ( redraw byte )
 	RTS
 
-@getmouse ( push y,x to stack )
-	,00 ,01 ,02 IOR ( grab y )
-	,00 ,00 ,02 IOR ( grab x )
-	RTS
-
-@putbyte ( print to console )
-	,00 IOW RTS 
-
 |d000 @ERROR BRK 
 |FFFA .RESET .FRAME .ERROR
diff --git a/examples/screen.usm b/examples/screen.usm
new file mode 100644
index 0000000..e92bd8e
--- /dev/null
+++ b/examples/screen.usm
@@ -0,0 +1,38 @@
+( screen )
+
+:dev/r fff8 ( std read port )
+:dev/w fff9 ( std write port )
+;width0
+;width1
+;height0
+;height1
+
+|0100 @RESET 
+	
+	( set read/write to dev/screen )
+	,01 DUP ,dev/r STR ,dev/w STR 
+
+	( load screen size )
+	,00 IOR^ ,width0 STR^
+	,02 IOR^ ,height0 STR^
+
+	( draw pixel at screen center )
+
+	,0101 
+	,width0 LDR^ ,0002 DIV^ 
+	,height0 LDR^ ,0002 DIV^ 
+	,putpixel JSR
+
+BRK
+
+|c000 @FRAME BRK
+
+@putpixel 
+	IOW^ ( y short )
+	IOW^ ( x short )
+	IOW ( color byte )
+	IOW ( redraw byte )
+	RTS
+
+|d000 @ERROR BRK 
+|FFFA .RESET .FRAME .ERROR
diff --git a/examples/test.usm b/examples/test.usm
index a4db0f6..2c82c86 100644
--- a/examples/test.usm
+++ b/examples/test.usm
@@ -1,13 +1,45 @@
 ( my default test file )
 
-;iterator
+:dev/r fff8 ( std read port )
+:dev/w fff9 ( std write port )
 
 |0100 @RESET 
+	
+	,02 ,dev/r STR ( set dev/read mouse#02 )
+	,01 ,dev/w STR ( set dev/write screen#01 )
 
-	,1234
+	,00 ,01 ,0001 ,0000 ,putpixel JSR
+	,00 ,01 ,0000 ,0001 ,putpixel JSR
+	,00 ,01 ,0002 ,0001 ,putpixel JSR
+	,01 ,02 ,0001 ,0002 ,putpixel JSR
 
 BRK
 
-|c000 @FRAME BRK
+|c000 @FRAME
+
+	( get mouse button, or break )
+	,04 IOR
+	,01 NEQ
+	BRK?
+		
+	( paint a white pixel )
+	,01 ,01 
+	,getmouse JSR
+	,putpixel JSR
+
+BRK
+
+@getmouse
+	,02 IOR^ ( get mouse y )
+	,00 IOR^ ( get mouse x )
+	RTS
+
+@putpixel 
+	IOW^ ( y short )
+	IOW^ ( x short )
+	IOW ( color byte )
+	IOW ( redraw byte )
+	RTS
+
 |d000 @ERROR BRK 
 |FFFA .RESET .FRAME .ERROR
diff --git a/uxn.c b/uxn.c
index 78bbb72..4ff5f47 100644
--- a/uxn.c
+++ b/uxn.c
@@ -19,13 +19,13 @@ WITH REGARD TO THIS SOFTWARE.
 
 void   setflag(Uint8 *st, char flag, int b) { if(b) *st |= flag; else *st &= (~flag); }
 int    getflag(Uint8 *st, char flag) { return *st & flag; }
-Uint16 bytes2short(Uint8 a, Uint8 b) { return (a << 8) + b; }
 void   wspush8(Uxn *u, Uint8 b) { u->wst.dat[u->wst.ptr++] = b; }
 Uint8  wspop8(Uxn *u) { return u->wst.dat[--u->wst.ptr]; }
 Uint8  wspeek8(Uxn *u, Uint8 o) { return u->wst.dat[u->wst.ptr - o]; }
+Uint8  mempeek8(Uxn *u, Uint16 s) { return u->ram.dat[s]; }
 void   wspush16(Uxn *u, Uint16 s) { wspush8(u,s >> 8); wspush8(u,s & 0xff); }
 Uint16 wspop16(Uxn *u) { return wspop8(u) + (wspop8(u) << 8); }
-Uint16 wspeek16(Uxn *u, Uint8 o) { return bytes2short(u->wst.dat[u->wst.ptr - o], u->wst.dat[u->wst.ptr - o + 1]); }
+Uint16 wspeek16(Uxn *u, Uint8 o) { return (u->wst.dat[u->wst.ptr - o] << 8) + u->wst.dat[u->wst.ptr - o + 1]; }
 void   rspush16(Uxn *u, Uint16 a) { u->rst.dat[u->rst.ptr++] = a; }
 Uint16 mempeek16(Uxn *u, Uint16 s) { return (u->ram.dat[s] << 8) + (u->ram.dat[s + 1] & 0xff); }
 
@@ -34,8 +34,8 @@ void op_brk(Uxn *u) { setflag(&u->status,FLAG_HALT, 1); }
 void op_li1(Uxn *u) { u->literal += 1; }
 void op_lix(Uxn *u) { u->literal += u->ram.dat[u->ram.ptr++]; }
 void op_nop(Uxn *u) { printf("NOP"); (void)u; }
-void op_ior(Uxn *u) { Uint8 devid = wspop8(u); Uint16 devop = wspop8(u); Device *dev = &u->dev[devid]; if(devid < u->devices) wspush8(u, dev->rfn(dev,devop)); }
-void op_iow(Uxn *u) { Uint8 devid = wspop8(u); Uint16 devop = wspop8(u); Device *dev = &u->dev[devid]; if(devid < u->devices) dev->wfn(dev,devop); }
+void op_ior(Uxn *u) { Device *dev = &u->dev[mempeek8(u, u->devr)]; if(dev) wspush8(u, dev->read(dev, wspop8(u))); }
+void op_iow(Uxn *u) { Uint8 a = wspop8(u); Device *dev = &u->dev[mempeek8(u, u->devw)]; if(dev) dev->write(dev, a); }
 void op_ldr(Uxn *u) { Uint16 a = wspop16(u); wspush8(u, u->ram.dat[a]); }
 void op_str(Uxn *u) { Uint16 a = wspop16(u); Uint8 b = wspop8(u); u->ram.dat[a] = b; }
 /* Logic */
@@ -60,6 +60,11 @@ void op_equ(Uxn *u) { Uint8 a = wspop8(u), b = wspop8(u); wspush8(u, b == a); }
 void op_neq(Uxn *u) { Uint8 a = wspop8(u), b = wspop8(u); wspush8(u, b != a); }
 void op_gth(Uxn *u) { Uint8 a = wspop8(u), b = wspop8(u); wspush8(u, b > a); }
 void op_lth(Uxn *u) { Uint8 a = wspop8(u), b = wspop8(u); wspush8(u, b < a); }
+/* --- */
+void op_ior16(Uxn *u) { Uint8 a = wspop8(u); Device *dev = &u->dev[mempeek8(u, u->devr)]; if(dev) wspush16(u, (dev->read(dev, a) << 8) + dev->read(dev, a + 1)); }
+void op_iow16(Uxn *u) { Uint8 a = wspop8(u); Uint8 b = wspop8(u); Device *dev = &u->dev[mempeek8(u, u->devw)]; if(dev) { dev->write(dev, b); dev->write(dev, a); } }
+void op_ldr16(Uxn *u) { Uint16 a = wspop16(u); wspush16(u, (u->ram.dat[a] << 8) + u->ram.dat[a + 1]); }
+void op_str16(Uxn *u) { Uint16 a = wspop16(u); Uint16 b = wspop16(u); u->ram.dat[a] = b >> 8; u->ram.dat[a + 1] = b & 0xff; }
 /* Stack(16-bits) */
 void op_pop16(Uxn *u) { wspop16(u); }
 void op_dup16(Uxn *u) { wspush16(u, wspeek16(u, 2)); }
@@ -84,15 +89,21 @@ void (*ops[])(Uxn *u) = {
 	op_jmp, op_jsr, op_nop, op_rts, op_nop, op_nop, op_nop, op_nop, 
 	op_pop, op_dup, op_swp, op_ovr, op_rot, op_and, op_ora, op_rol,
 	op_add, op_sub, op_mul, op_div, op_equ, op_neq, op_gth, op_lth,
+	/* 16-bit */
+	op_brk, op_nop, op_li1, op_lix, op_ior16, op_iow16, op_ldr16, op_str16, 
+	op_jmp, op_jsr, op_nop, op_rts, op_nop, op_nop, op_nop, op_nop, 
 	op_pop16, op_dup16, op_swp16, op_ovr16, op_rot16, op_and16, op_ora16, op_rol16,
 	op_add16, op_sub16, op_mul16, op_div16, op_equ16, op_neq16, op_gth16, op_lth16
 };
 
 Uint8 opr[][2] = { 
-	{0,0}, {0,0}, {0,0}, {0,0}, {2,1}, {2,0}, {2,1}, {3,0},
+	{0,0}, {0,0}, {0,0}, {0,0}, {1,1}, {1,0}, {2,1}, {3,0},
 	{2,0}, {2,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0},
 	{1,0}, {1,2}, {2,2}, {3,3}, {3,3}, {2,1}, {2,1}, {2,1},
 	{2,1}, {2,1}, {2,1}, {2,1}, {2,1}, {2,1}, {2,1}, {2,1},
+	/* 16-bit */
+	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, /* TODO */
+	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, /* TODO */
 	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, /* TODO */
 	{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}  /* TODO */
 };
@@ -124,7 +135,7 @@ opcuxn(Uxn *u, Uint8 instr)
 	setflag(&u->status, FLAG_SIGN, (instr >> 6) & 1); /* usused */
 	setflag(&u->status, FLAG_COND, (instr >> 7) & 1);
 	if(getflag(&u->status, FLAG_SHORT))
-		op += 16;
+		op += 32;
 	if(u->wst.ptr < opr[op][0])
 		return haltuxn(u, "Stack underflow", op);
 	if(u->wst.ptr + opr[op][1] - opr[op][0] >= 255)
@@ -174,6 +185,8 @@ loaduxn(Uxn *u, char *filepath)
 	if(!(f = fopen(filepath, "rb")))
 		return haltuxn(u, "Missing input.", 0);
 	fread(u->ram.dat, sizeof(u->ram.dat), 1, f);
+	u->devr = 0xfff8;
+	u->devw = 0xfff9;
 	u->vreset = mempeek16(u, 0xfffa);
 	u->vframe = mempeek16(u, 0xfffc);
 	u->verror = mempeek16(u, 0xfffe);
@@ -188,11 +201,11 @@ loaduxn(Uxn *u, char *filepath)
 /* to start: evaluxn(u, u->vreset); */
 
 Device *
-portuxn(Uxn *u, char *name, Uint8 (*onread)(Device *, Uint8), Uint8 (*onwrite)(Device *, Uint8))
+portuxn(Uxn *u, char *name, Uint8 (*rfn)(Device *, Uint8), Uint8 (*wfn)(Device *, Uint8))
 {
 	Device *d = &u->dev[u->devices++];
-	d->rfn = onread;
-	d->wfn = onwrite;
+	d->read = rfn;
+	d->write = wfn;
 	d->len = 0;
 	printf("Device#%d: %s \n", u->devices, name);
 	return d;
diff --git a/uxn.h b/uxn.h
index bab691d..378cdc3 100644
--- a/uxn.h
+++ b/uxn.h
@@ -36,13 +36,13 @@ typedef struct {
 
 typedef struct Device {
 	Uint8 len, mem[8];
-	Uint8 (*rfn)(struct Device *, Uint8);
-	Uint8 (*wfn)(struct Device *, Uint8);
+	Uint8 (*read)(struct Device *, Uint8);
+	Uint8 (*write)(struct Device *, Uint8);
 } Device;
 
 typedef struct {
 	Uint8 literal, status, devices;
-	Uint16 counter, vreset, vframe, verror;
+	Uint16 counter, devr, devw, vreset, vframe, verror;
 	Stack8 wst;
 	Stack16 rst;
 	Memory ram;
@@ -54,4 +54,4 @@ int getflag(Uint8 *status, char flag);
 int loaduxn(Uxn *c, char *filepath);
 int bootuxn(Uxn *c);
 int evaluxn(Uxn *u, Uint16 vec);
-Device *portuxn(Uxn *u, char *name, Uint8 (*onread)(Device *, Uint8), Uint8 (*onwrite)(Device *, Uint8));
+Device *portuxn(Uxn *u, char *name, Uint8 (*rfn)(Device *, Uint8), Uint8 (*wfn)(Device *, Uint8));