diff --git a/build.sh b/build.sh
index 4f80a48..64dffc1 100755
--- a/build.sh
+++ b/build.sh
@@ -3,7 +3,7 @@
 # format code
 # clang-format -i src/porporo.c src/devices/*
 
-SRC="src/uxn.c src/devices/system.c src/devices/screen.c src/devices/controller.c src/devices/mouse.c src/devices/datetime.c src/porporo.c"
+SRC="src/uxn.c src/devices/system.c src/devices/screen.c src/devices/controller.c src/devices/mouse.c src/devices/file.c src/devices/datetime.c src/porporo.c"
 
 # remove old
 rm -f bin/porporo
diff --git a/src/devices/file.c b/src/devices/file.c
new file mode 100644
index 0000000..cd83bde
--- /dev/null
+++ b/src/devices/file.c
@@ -0,0 +1,287 @@
+#define _XOPEN_SOURCE 500
+#include <stdio.h>
+#include <dirent.h>
+#include <errno.h>
+#include <limits.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#ifdef _WIN32
+#include <libiberty/libiberty.h>
+#define realpath(s, dummy) lrealpath(s)
+#define DIR_SEP_CHAR '\\'
+#define DIR_SEP_STR "\\"
+#define pathcmp(path1, path2, length) strncasecmp(path1, path2, length) /* strncasecmp provided by libiberty */
+#define notdriveroot(file_name) (file_name[0] != DIR_SEP_CHAR && ((strlen(file_name) > 2 && file_name[1] != ':') || strlen(file_name) <= 2))
+#else
+#define DIR_SEP_CHAR '/'
+#define DIR_SEP_STR "/"
+#define pathcmp(path1, path2, length) strncmp(path1, path2, length)
+#define notdriveroot(file_name) (file_name[0] != DIR_SEP_CHAR)
+#endif
+
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
+
+#include "../uxn.h"
+#include "file.h"
+
+/*
+Copyright (c) 2021-2023 Devine Lu Linvega, Andrew Alderwick
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE.
+*/
+
+typedef struct {
+	FILE *f;
+	DIR *dir;
+	char current_filename[4096];
+	struct dirent *de;
+	enum { IDLE,
+		FILE_READ,
+		FILE_WRITE,
+		DIR_READ } state;
+	int outside_sandbox;
+} UxnFile;
+
+static UxnFile uxn_file[POLYFILEY];
+
+static void
+reset(UxnFile *c)
+{
+	if(c->f != NULL) {
+		fclose(c->f);
+		c->f = NULL;
+	}
+	if(c->dir != NULL) {
+		closedir(c->dir);
+		c->dir = NULL;
+	}
+	c->de = NULL;
+	c->state = IDLE;
+	c->outside_sandbox = 0;
+}
+
+static Uint16
+get_entry(char *p, Uint16 len, const char *pathname, const char *basename, int fail_nonzero)
+{
+	struct stat st;
+	if(len < strlen(basename) + 8)
+		return 0;
+	if(stat(pathname, &st))
+		return fail_nonzero ? snprintf(p, len, "!!!! %s\n", basename) : 0;
+	else if(S_ISDIR(st.st_mode))
+		return snprintf(p, len, "---- %s/\n", basename);
+	else if(st.st_size < 0x10000)
+		return snprintf(p, len, "%04x %s\n", (unsigned int)st.st_size, basename);
+	else
+		return snprintf(p, len, "???? %s\n", basename);
+}
+
+static Uint16
+file_read_dir(UxnFile *c, char *dest, Uint16 len)
+{
+	static char pathname[4352];
+	char *p = dest;
+	if(c->de == NULL) c->de = readdir(c->dir);
+	for(; c->de != NULL; c->de = readdir(c->dir)) {
+		Uint16 n;
+		if(c->de->d_name[0] == '.' && c->de->d_name[1] == '\0')
+			continue;
+		if(strcmp(c->de->d_name, "..") == 0) {
+			/* hide "sandbox/.." */
+			char cwd[PATH_MAX] = {'\0'}, *t;
+			/* Note there's [currently] no way of chdir()ing from uxn, so $PWD
+			 * is always the sandbox top level. */
+			getcwd(cwd, sizeof(cwd));
+			/* We already checked that c->current_filename exists so don't need a wrapper. */
+			t = realpath(c->current_filename, NULL);
+			if(strcmp(cwd, t) == 0) {
+				free(t);
+				continue;
+			}
+			free(t);
+		}
+		if(strlen(c->current_filename) + 1 + strlen(c->de->d_name) < sizeof(pathname))
+			snprintf(pathname, sizeof(pathname), "%s/%s", c->current_filename, c->de->d_name);
+		else
+			pathname[0] = '\0';
+		n = get_entry(p, len, pathname, c->de->d_name, 1);
+		if(!n) break;
+		p += n;
+		len -= n;
+	}
+	return p - dest;
+}
+
+static char *
+retry_realpath(const char *file_name)
+{
+	char *r, p[PATH_MAX] = {'\0'}, *x;
+	int fnlen;
+	if(file_name == NULL) {
+		errno = EINVAL;
+		return NULL;
+	} else if((fnlen = strlen(file_name)) >= PATH_MAX) {
+		errno = ENAMETOOLONG;
+		return NULL;
+	}
+	if(notdriveroot(file_name)) {
+		/* TODO: use a macro instead of '/' for absolute path first character so that other systems can work */
+		/* if a relative path, prepend cwd */
+		getcwd(p, sizeof(p));
+		if(strlen(p) + strlen(DIR_SEP_STR) + fnlen >= PATH_MAX) {
+			errno = ENAMETOOLONG;
+			return NULL;
+		}
+		strcat(p, DIR_SEP_STR); /* TODO: use a macro instead of '/' for the path delimiter */
+	}
+	strcat(p, file_name);
+	while((r = realpath(p, NULL)) == NULL) {
+		if(errno != ENOENT)
+			return NULL;
+		x = strrchr(p, DIR_SEP_CHAR); /* TODO: path delimiter macro */
+		if(x)
+			*x = '\0';
+		else
+			return NULL;
+	}
+	return r;
+}
+
+static void
+file_check_sandbox(UxnFile *c)
+{
+	char *x, *rp, cwd[PATH_MAX] = {'\0'};
+	x = getcwd(cwd, sizeof(cwd));
+	rp = retry_realpath(c->current_filename);
+	if(rp == NULL || (x && pathcmp(cwd, rp, strlen(cwd)) != 0)) {
+		c->outside_sandbox = 1;
+		fprintf(stderr, "file warning: blocked attempt to access %s outside of sandbox\n", c->current_filename);
+	}
+	free(rp);
+}
+
+static Uint16
+file_init(UxnFile *c, char *filename, size_t max_len, int override_sandbox)
+{
+	char *p = c->current_filename;
+	size_t len = sizeof(c->current_filename);
+	reset(c);
+	if(len > max_len) len = max_len;
+	while(len) {
+		if((*p++ = *filename++) == '\0') {
+			if(!override_sandbox) /* override sandbox for loading roms */
+				file_check_sandbox(c);
+			return 0;
+		}
+		len--;
+	}
+	c->current_filename[0] = '\0';
+	return 0;
+}
+
+static Uint16
+file_read(UxnFile *c, void *dest, int len)
+{
+	if(c->outside_sandbox) return 0;
+	if(c->state != FILE_READ && c->state != DIR_READ) {
+		reset(c);
+		if((c->dir = opendir(c->current_filename)) != NULL)
+			c->state = DIR_READ;
+		else if((c->f = fopen(c->current_filename, "rb")) != NULL)
+			c->state = FILE_READ;
+	}
+	if(c->state == FILE_READ)
+		return fread(dest, 1, len, c->f);
+	if(c->state == DIR_READ)
+		return file_read_dir(c, dest, len);
+	return 0;
+}
+
+static Uint16
+file_write(UxnFile *c, void *src, Uint16 len, Uint8 flags)
+{
+	Uint16 ret = 0;
+	if(c->outside_sandbox) return 0;
+	if(c->state != FILE_WRITE) {
+		reset(c);
+		if((c->f = fopen(c->current_filename, (flags & 0x01) ? "ab" : "wb")) != NULL)
+			c->state = FILE_WRITE;
+	}
+	if(c->state == FILE_WRITE) {
+		if((ret = fwrite(src, 1, len, c->f)) > 0 && fflush(c->f) != 0)
+			ret = 0;
+	}
+	return ret;
+}
+
+static Uint16
+file_stat(UxnFile *c, void *dest, Uint16 len)
+{
+	char *basename = strrchr(c->current_filename, DIR_SEP_CHAR);
+	if(c->outside_sandbox) return 0;
+	if(basename != NULL)
+		basename++;
+	else
+		basename = c->current_filename;
+	return get_entry(dest, len, c->current_filename, basename, 0);
+}
+
+static Uint16
+file_delete(UxnFile *c)
+{
+	return c->outside_sandbox ? 0 : unlink(c->current_filename);
+}
+
+/* IO */
+
+void
+file_deo(Program *prg, Uint8 id, Uint8 *ram, Uint8 *d, Uint8 port)
+{
+	UxnFile *c = &uxn_file[id];
+	Uint16 addr, len, res;
+	switch(port) {
+	case 0x5:
+		addr = PEEK2(d + 0x4);
+		len = PEEK2(d + 0xa);
+		if(len > 0x10000 - addr)
+			len = 0x10000 - addr;
+		res = file_stat(c, &ram[addr], len);
+		POKE2(d + 0x2, res);
+		break;
+	case 0x6:
+		res = file_delete(c);
+		POKE2(d + 0x2, res);
+		break;
+	case 0x9:
+		addr = PEEK2(d + 0x8);
+		res = file_init(c, (char *)&ram[addr], 0x10000 - addr, 0);
+		POKE2(d + 0x2, res);
+		break;
+	case 0xd:
+		addr = PEEK2(d + 0xc);
+		len = PEEK2(d + 0xa);
+		if(len > 0x10000 - addr)
+			len = 0x10000 - addr;
+		res = file_read(c, &ram[addr], len);
+		POKE2(d + 0x2, res);
+		break;
+	case 0xf:
+		addr = PEEK2(d + 0xe);
+		len = PEEK2(d + 0xa);
+		if(len > 0x10000 - addr)
+			len = 0x10000 - addr;
+		res = file_write(c, &ram[addr], len, d[0x7]);
+		POKE2(d + 0x2, res);
+		break;
+	}
+}
diff --git a/src/devices/file.h b/src/devices/file.h
new file mode 100644
index 0000000..9ed2efd
--- /dev/null
+++ b/src/devices/file.h
@@ -0,0 +1,19 @@
+/*
+Copyright (c) 2021 Devine Lu Linvega, Andrew Alderwick
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE.
+*/
+
+#define FILE_VERSION 1
+#define FILE_DEIMASK 0x0000
+#define FILE_DEOMASK 0xa260
+
+#define POLYFILEY 2
+#define DEV_FILE0 0xa
+
+void file_deo(Program *prg, Uint8 id, Uint8 *ram, Uint8 *d, Uint8 port);
diff --git a/src/porporo.c b/src/porporo.c
index 32b7011..3cd6536 100644
--- a/src/porporo.c
+++ b/src/porporo.c
@@ -6,6 +6,7 @@
 #include "devices/screen.h"
 #include "devices/controller.h"
 #include "devices/mouse.h"
+#include "devices/file.h"
 #include "devices/datetime.h"
 
 /*
@@ -31,7 +32,7 @@ static Uint8 *ram;
 static int plen;
 
 static int reqdraw;
-static int dragx, dragy, movemode = 1;
+static int dragx, dragy, movemode;
 static int camerax, cameray;
 
 static SDL_Window *gWindow = NULL;
@@ -353,6 +354,10 @@ static void
 handle_mouse(SDL_Event *event)
 {
 	int i, desk = 1, x = event->motion.x - camerax, y = event->motion.y - cameray;
+	if(event->type == SDL_MOUSEWHEEL) {
+		mouse_scroll(&focused->u, &focused->u.dev[0x90], event->wheel.x, event->wheel.y);
+		return;
+	}
 	for(i = plen - 1; i; i--) {
 		Program *p = &programs[i];
 		if(withinprogram(p, x, y)) {
@@ -373,8 +378,6 @@ handle_mouse(SDL_Event *event)
 					mouse_down(&p->u, &p->u.dev[0x90], SDL_BUTTON(event->button.button));
 				else if(event->type == SDL_MOUSEBUTTONUP)
 					mouse_up(&p->u, &p->u.dev[0x90], SDL_BUTTON(event->button.button));
-				else if(event->type == SDL_MOUSEWHEEL)
-					mouse_scroll(&p->u, &p->u.dev[0x90], event->wheel.x, event->wheel.y);
 				return;
 			}
 		}
@@ -395,6 +398,7 @@ handle_mouse(SDL_Event *event)
 static void
 domouse(SDL_Event *event)
 {
+
 	switch(event->type) {
 	case SDL_MOUSEBUTTONDOWN: handle_mouse(event); break;
 	case SDL_MOUSEMOTION: handle_mouse(event); break;
@@ -529,6 +533,8 @@ emu_deo(Uxn *u, Uint8 addr, Uint8 value)
 	case 0x20:
 		screen_deo(prg, u->ram, &u->dev[d], p);
 		break;
+	case 0xa0: file_deo(prg, 0, u->ram, &u->dev[d], p); break;
+	case 0xb0: file_deo(prg, 1, u->ram, &u->dev[d], p); break;
 	}
 }
 
@@ -550,7 +556,6 @@ porporo_key(char c)
 	switch(c) {
 	case 'd':
 		movemode = !movemode;
-		printf("%d\n", movemode);
 		break;
 	}
 }
@@ -577,6 +582,7 @@ main(int argc, char **argv)
 	addprogram(20, 30, "bin/screen.pixel.rom");
 	addprogram(150, 90, "bin/oekaki.rom");
 	addprogram(650, 160, "bin/catclock.rom");
+	addprogram(750, 300, "bin/left.rom");
 
 	connectports(prg_hello, prg_listen, 0x12, 0x18);
 	connectports(prg_listen, porporo, 0x12, 0x18);
@@ -600,9 +606,12 @@ main(int argc, char **argv)
 		while(SDL_PollEvent(&event) != 0) {
 			switch(event.type) {
 			case SDL_QUIT: quit(); break;
+			case SDL_MOUSEWHEEL:
 			case SDL_MOUSEBUTTONUP:
 			case SDL_MOUSEBUTTONDOWN:
-			case SDL_MOUSEMOTION: domouse(&event); break;
+			case SDL_MOUSEMOTION:
+				domouse(&event);
+				break;
 			case SDL_TEXTINPUT:
 				if(focused == porporo) {
 					porporo_key(event.text.text[0]);