The map editor is in Picture mode (also known as "Tilemap mode").

F2 switch to picture mode
F3 switch to passability mode
F4 switch to door placement mode
F5 switch to NPC placement mode
F6 switch to foemap mode

Use the arrow keys to move around the map.

Use SHIFT+arrow keys to move around the map faster.

Along the top of the screen you will see a row of maptiles, with your currently selected maptile highlighted. You can press < and > to change your selected maptile, or press ENTER to bring up a full-screen maptile picker.

Press the SPACE bar to place a maptile on the map.

Press CAPSLOCK if you want to choose the tile under the cursor as the current tile to place.

CTRL+F fills the screen with the current tile.

CTRL+P does a "paint-bucket" style fill using the current tile.

CTRL+R replaces all tiles like the one under the cursor with the currently selected tile.

~ shows a small preview of the entire map.

TAB toggles a blue rectangle that shows roughly what portion of the map you are currently looking at.

CTRL+H moves the hero's starting location to this location on this map. Remember that only one map in your game needs a hero starting location.

Press 1 or 2 to make the tile under the cursor animate using animation pattern 0 or 1.

Hold CTRL and press 1 or 2 to make all tiles on the map like the one under the cursor animate using animation pattern 0 or 1.

CTRL+D toggles whether default tile passability will be used for any new tiles that you place.

CTRL+L opens the Layer menu, where you can change tilesets and layer visibility.

PageUp and PageDown change which layer you are working on. Remember that layer 0 is the bottommost.

CTRL+J makes the current layer jiggle. This can be useful to visually distinguish a layer you are working on from another layer that covers it up. Press CTRL+J again to stop the jiggling.

ALT+a number disables or enables that layer (you can't disable layer 0). Disabled layers aren't drawn while editing or playing.