The map editor is in Passability mode (also known as "Wallmap 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
F7 switch to zonemap mode

Use the arrow keys to move around the map.

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

Use ALT+arrow keys to move the view of the map.

While you are in passability mode, you will see thick flashing lines that indicate where walls are located.

At the top right corner the current drawing tool is shown. The tools are:

D - Draw tool:
  Press one of the keys to modify
  walls that are described below (see
  "Drawing Keys"), or press and hold
  down SPACE while moving the cursor
  to draw walls in a line.

B - Box tool:
  Press SPACE once to place one
  corner of a rectangle, move the
  cursor to the opposite corner, and
  then press one of the Drawing Keys
  to modify the walls for all tiles
  in the box.

P - Paint on Layer # tool:
  Finds the continuous area on the
  current tilemap layer under the
  cursor, and changes the walls for
  all those tiles according to the
  Drawing Key pressed; like a flood
  fill of a map layer except that the
  map layer isn't modified. You can
  use PageDown and PageUp to change
  the selected layer. For example,
  you can use this to cover a puddle
  of acid with harmtiles by pressing
  H.

M - Mark tool:
  Use to select a rectangular of the
  map to copy. Press SPACE once to
  place one corner of the rectangle,
  and SPACE a second time at the
  opposite corner. The tool will then
  be changed to the Clone tool. Mark
  copies the visible tilemap layers,
  wallmap, foemap, and zones in the
  rectangle.

C - Clone tool:
  Press SPACE to paste a selection
  copied with the Mark tool.  You can
  switch to different editing modes
  to preview the changes to walls,
  foemap, and zones.  If default
  passability is on (press CTRL+D to
  toggle), the wallmap will updated
  using default walls instead of the
  copied walls.  Only visible map
  layers are modified (press ALT+~ to
  toggle visibility of the current
  map layer), so a map layer has to
  be visible both when Marking and
  when Cloning.

Drawing Keys:

Press SPACE to make the tile under the cursor fully impassable in all four directions. Press SPACE again to remove the walls and make the tile passable.

CTRL+Up makes the selected tile impassable on the top.

CTRL+Down makes the selected tile impassable on the bottom.

CTRL+Left makes the selected tile impassable on the left side.

CTRL+Right makes the selected tile impassable on the right side.

H marks the tile as a harm tile that can damage heroes when the player steps on it.

CTRL+A marks the tile as special for Airships (or other vehicle or scripting purposes).

CTRL+B marks the tile as special for Boats (or other vehicle or scripting purposes).

O marks the tile as overhead. This is obsolete. You should create a tilemap layer and place it above heroes and NPCs (in the Layers and Tilesets menu) instead if you want make tiles overhead.


Other Controls:

CTRL+Z undoes a change to the tilemap, wallmap, foemap or zonemap. Changes to NPCs and doors are not undoable. The undo history buffer is near-infinite, but certain things cause it to be cleared: resizing the map, deleting or swapping map layers, erasing map data, and leaving the map editor.

CTRL+Y redoes an undone change.

CTRL+S immediately saves, useful when live-previewing a game.

CTRL+W paints the tiles visible in the window/screen using the last Drawing Key used.

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

~ shows a preview of the entire map.