ASCII art game with trains and time:

First, each level is ASCII art, sort of like Rail:

-	Horizontal rail
|	Vertical rail
/	Ascending rail
\	Descending rail
*	Universal junction
+	HV junction
x	Diagonal junction
v^<>	Y junctions
$	Train starts here, southeast
#	Train ends here
@	Reflector

Each train is a little 8x8 bitmap -- no that's too small,
maybe 16x16? -- with a number from 0 to 9 on it, also a
direction, and an arrow pointing toward its left or its
right. The arrow indicates the direction it will take next
time it comes to a Y junction. You can change this direction
by pressing a key from 0 to 9 corresponding to the number on
the train. Get it?

The idea is to get all the trains to gracefully end
somewhere. Without crashing, and without, of course, running
out of time.

Now I just need to make a 16x16 font, and the rest should
come easy.

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I've decided instead to use the 8x8 font, and just have
really tiny graphics. Also, all the graphics will be
monochrome, so I can color them with draw_character_ex at
runtime. I'll draw a train, then a number over it. The train
images are:

	Horiz dir	Vert dir	Turning
	---------	--------	-------
_dl	None		Down		Left
_dr	None		Down		Right
_ul	None		Up		Left
_ur	None		Up		Right
l_l	Left		None		Left
l_r	Left		None		Right
ldl	Left		Down		Left
ldr	Left		Down		Right
lul	Left		Up		Left
lur	Left		Up		Right
r_l	Right		None		Left
r_r	Right		None		Right
rdl	Right		Down		Left
rdr	Right		Down		Right
rul	Right		Up		Left
rur	Right		Up		Right

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Ideas for improving the game:

 * A ball is travelling freely, except when it goes onto
tracks, it has to follow them to the end. It destroys the
tracks. All the tracks must be destroyed before a time bomb
explodes.
 * 24x24 graphics.
 * Just one train, not 10, and you control its turning, and
it is on a randomly arranged set of tracks, shooting at
enemies to increase time before time runs out.
