diff --git a/CMakeLists.txt b/CMakeLists.txt
index 02646a0..9b72d22 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,12 +15,14 @@ set(SOURCES
 	src/draw.c
 	src/input.c
 	src/level.c
+	src/editor.c
 	src/player.c
 	src/polarity.c
 )
 
 set(ASSETS
 	res/tileset.png
+	res/editor_cursor.png
 	res/test.kble
 	res/burn.kble
 	res/bounce.kble
diff --git a/inc/editor.h b/inc/editor.h
new file mode 100644
index 0000000..a37cfa5
--- /dev/null
+++ b/inc/editor.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void editor(void);
diff --git a/inc/input.h b/inc/input.h
index 9cf7c81..e4676e7 100644
--- a/inc/input.h
+++ b/inc/input.h
@@ -1,6 +1,18 @@
 #pragma once
 
-enum Key { K_LEFT, K_RIGHT, K_UP, K_DOWN, K_JUMP, K_POLARITY, K_EXIT, K_COUNT };
+enum Key {
+	K_LEFT,
+	K_RIGHT,
+	K_UP,
+	K_DOWN,
+	K_JUMP,
+	K_POLARITY,
+	K_EXIT,
+	K_EDITOR,
+	K_SCROLL_UP,
+	K_SCROLL_DOWN,
+	K_COUNT
+};
 enum KeyState { KS_UP, KS_DOWN, KS_PRESS };
 
 struct Input {
diff --git a/inc/level.h b/inc/level.h
index 8c1790d..1777a64 100644
--- a/inc/level.h
+++ b/inc/level.h
@@ -28,11 +28,14 @@ void level_deinit(void);
 
 void level_load(int id);
 void level_reload(void);
-void level_regen_visual_data(void);
+void level_regen_visual_data(int editing);
 void level_next(void);
 
 void level_draw(void);
+void level_draw_name(void);
 
 int level_get(int x, int y);
 int level_get_px(int x, int y);
+void level_set(int x, int y, int v);
 struct Vec level_find(enum Tile);
+struct Vec level_dim(void);
diff --git a/inc/tile.h b/inc/tile.h
index 74862a6..82c77fa 100644
--- a/inc/tile.h
+++ b/inc/tile.h
@@ -13,5 +13,6 @@ enum Tile {
 	TILE_GRAV_U,
 	TILE_GRAV_R,
 	TILE_GRAV_L,
+	TILE_COUNT,
 	TILE_OOB,
 };
diff --git a/res/editor_cursor.png b/res/editor_cursor.png
new file mode 100644
index 0000000..6ce82c7
Binary files /dev/null and b/res/editor_cursor.png differ
diff --git a/src/editor.c b/src/editor.c
new file mode 100644
index 0000000..598ec4b
--- /dev/null
+++ b/src/editor.c
@@ -0,0 +1,100 @@
+#include "editor.h"
+#include "conf.h"
+#include "input.h"
+#include "level.h"
+#include "tile.h"
+#include "vec.h"
+#include <gint/display.h>
+
+static int cx, cy;
+static int ctile = 1;
+
+static void editor_update(void);
+static void editor_draw(void);
+static void draw_grid(void);
+static void draw_cursor(void);
+
+void
+editor(void)
+{
+	extern volatile int has_ticked;
+	level_regen_visual_data(1);
+	do {
+		editor_draw();
+		editor_update();
+	} while (!input_pressed(K_EDITOR));
+	has_ticked = 0;
+	level_regen_visual_data(0);
+}
+
+static void
+editor_update(void)
+{
+	const struct Vec dim = level_dim();
+
+	input_update();
+
+	/* move cursor */
+	cx += input_pressed(K_RIGHT) - input_pressed(K_LEFT);
+	cy += input_pressed(K_DOWN) - input_pressed(K_UP);
+	cx %= dim.x;
+	cx += dim.x * (cx < 0);
+	cy %= dim.y;
+	cy += dim.y * (cy < 0);
+
+	/* select tile */
+	ctile += input_pressed(K_SCROLL_UP) - input_pressed(K_SCROLL_DOWN);
+	ctile += (TILE_COUNT - 1) * (ctile < 1);
+	ctile %= TILE_COUNT;
+	ctile += !ctile;
+
+	/* change the world */
+	if (input_down(K_JUMP)) {
+		level_set(cx, cy, ctile);
+		level_regen_visual_data(1);
+	}
+	if (input_down(K_POLARITY)) {
+		level_set(cx, cy, 0);
+		level_regen_visual_data(1);
+	}
+}
+
+static void
+editor_draw(void)
+{
+	dclear(C_BLACK);
+	level_draw();
+	draw_cursor();
+	draw_grid();
+	dupdate();
+}
+
+static void
+draw_grid(void)
+{
+	int i;
+
+	/* hlines */
+	i = 0;
+	while (i += TILE_SIZE, i < DHEIGHT)
+		dhline(i, C_BLUE);
+
+	/* vlines */
+	i = DRAW_OFF_X;
+	while (i += TILE_SIZE, i < DWIDTH)
+		dvline(i, C_BLUE);
+}
+
+static void
+draw_cursor(void)
+{
+	const int dx = cx * TILE_SIZE + DRAW_OFF_X;
+	const int dy = cy * TILE_SIZE;
+	extern bopti_image_t bimg_editor_cursor, bimg_tileset;
+	const int tileset_width = bimg_tileset.width / TILE_SIZE;
+
+	dimage(dx - TILE_SIZE / 2, dy - TILE_SIZE / 2, &bimg_editor_cursor);
+	dsubimage(dx, dy, &bimg_tileset, ctile % tileset_width * TILE_SIZE,
+	          (int)(ctile / tileset_width) * TILE_SIZE, TILE_SIZE,
+	          TILE_SIZE, 0);
+}
diff --git a/src/input.c b/src/input.c
index 72f05e6..1846a8c 100644
--- a/src/input.c
+++ b/src/input.c
@@ -3,7 +3,8 @@
 
 static struct Input input;
 static const int default_map[K_COUNT] = {
-    KEY_LEFT, KEY_RIGHT, KEY_UP, KEY_DOWN, KEY_SHIFT, KEY_ALPHA, KEY_EXIT};
+    KEY_LEFT,  KEY_RIGHT, KEY_UP, KEY_DOWN, KEY_SHIFT,
+    KEY_ALPHA, KEY_EXIT,  KEY_F3, KEY_F2,   KEY_F1};
 
 void
 input_init(void)
diff --git a/src/level.c b/src/level.c
index 2bc538c..866c3be 100644
--- a/src/level.c
+++ b/src/level.c
@@ -53,7 +53,7 @@ level_load(int id)
 	while (i-- > 0)
 		level.data[i] = b->data[i];
 	polarity_reset();
-	level_regen_visual_data();
+	level_regen_visual_data(0);
 	player_spawn(level.player);
 }
 
@@ -73,7 +73,7 @@ level_next(void)
 }
 
 void
-level_regen_visual_data(void)
+level_regen_visual_data(int editing)
 {
 	const int tileset_width = bimg_tileset.width / TILE_SIZE;
 	int y = level.height;
@@ -88,6 +88,7 @@ level_regen_visual_data(void)
 			vd->img_x = tile % tileset_width * TILE_SIZE;
 			vd->img_y = (int)(tile / tileset_width) * TILE_SIZE;
 			vd->visible = tile != 0;
+			if (editing) continue;
 			switch (tile) {
 			case TILE_RED:
 				vd->img_y += polarity() ? TILE_SIZE : 0;
@@ -114,8 +115,11 @@ level_draw(void)
 			          0);
 		}
 	}
+}
 
-	/* level name */
+void
+level_draw_name(void)
+{
 	dprint_opt(DWIDTH - 4, DHEIGHT - 2, C_BLACK, C_NONE, DTEXT_RIGHT,
 	           DTEXT_BOTTOM, "%s", levels[level.id].name);
 }
@@ -134,6 +138,13 @@ level_get_px(int x, int y)
 	return level_get(x / TILE_SIZE, y / TILE_SIZE);
 }
 
+void
+level_set(int x, int y, int v)
+{
+	if (x < 0 || y < 0 || x >= level.width || y >= level.height) return;
+	level.data[x + y * level.width] = v;
+}
+
 struct Vec
 level_find(enum Tile t)
 {
@@ -143,6 +154,12 @@ level_find(enum Tile t)
 	return (struct Vec){i % level.width, i / level.width};
 }
 
+struct Vec
+level_dim(void)
+{
+	return (struct Vec){level.width, level.height};
+}
+
 static void
 level_free(void)
 {
diff --git a/src/main.c b/src/main.c
index 1532b01..81f7588 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,4 +1,5 @@
 #include "conf.h"
+#include "editor.h"
 #include "input.h"
 #include "level.h"
 #include "player.h"
@@ -8,7 +9,7 @@
 
 static struct Player player;
 static int timer;
-static volatile int has_ticked;
+volatile int has_ticked;
 
 static void init(void);
 static void deinit(void);
@@ -68,6 +69,8 @@ update(void)
 {
 	input_update();
 	player_update(&player);
+	/* enter editor */
+	if (input_pressed(K_EDITOR)) editor();
 }
 
 static void
@@ -76,6 +79,7 @@ draw(void)
 	dclear(C_BLACK);
 	level_draw();
 	player_draw(&player);
+	level_draw_name();
 	dupdate();
 }
 
diff --git a/src/polarity.c b/src/polarity.c
index f24905e..37a2eaf 100644
--- a/src/polarity.c
+++ b/src/polarity.c
@@ -13,7 +13,7 @@ void
 polarity_invert(void)
 {
 	pol = !pol;
-	level_regen_visual_data();
+	level_regen_visual_data(0);
 }
 
 void