How this window works
In a game this shows the map being played, with every worm on it live (the one whose turn it is ringed); in the lobby, the map picked there. Draw (or Line): walls over openings the heat map should not lead through (the worm can still go there); the Eraser rubs out parts of them, Delete wall a whole one. Start (S) / Finish (F): click or drag where WAI starts and where it finishes. Save: the heat map is worked out now, and when the game loads this map WAI takes the finish, its team and the heat map from here.
Thought tree: WAI's last dream batch replayed fast -- every tiny worm is a copy of WAI racing its next turn. Flow: the colours stream the way the heat map leads to the finish. Right-drag (or Move) moves the view, the wheel zooms.
Draw: hold Shift to draw a straight horizontal or vertical line. Line (L): press at one end and let go at the other for one straight wall at any angle; hold Shift to keep it at 0, 45 or 90 degrees, Ctrl-click or Alt-click to carry on from the last line's end. Eraser (E): rub out only the parts of walls under its round brush (its size beside the tools; Shift keeps it on a straight line); Delete wall, or an Alt-click with the Eraser, takes a whole wall away. Undo takes back one drag or click at a time. A save that takes saved walls away says first what it will do.