		     PLAYING MOONLANDER (LEM)


The object of moonlander is to land a lunar module on the
surface of the moon.  The program will run on any 8K GT40
with a light pen and a clock.  If you are attached to a PDP-10
you may use the ROM bootstrap to bring over the assembled
binary.  If you are not "talking" to a PDP-10, you may load
in the binary loader (absolute loader) and load in the paper
tape version of the program.  Note: the program will destroy
the binary loader when it starts running.

When the program is loaded, it will automatically start and
display an "introductory message" on the screen.  Future
restart of the program will not cause this message to be
displayed.  Should any problems occur, the program may be
restarted at any time at location zero (000000).  Power fail
protection is also provided.  After starting (or restarting),
you then start playing the actual game.  All numbers, speeds,
weights, etc., are actual numbers.  They are for real.  To
make the game more possible for an average person to play, I
have given him about 25 to 50% more fuel in the final stages
of landing than he would actually have.

What the user sees on the screen is a broad and extremely
mountainous view of the moon.  On the right is a list of data
parameters which the user may examine.  They are height,
altitude, angle, fuel left, thrust, weight, horizontal velocity,
vertical velocity, horizontal acceleration, vertical accelera-
tion, distance and seconds.  At the top of the screen, any
four of the values may be displayed.  To display an item, the
user points the light pen at the item he wishes to display.
The item will then start blinking, to indicate that this is the
item to be displayed.  The user then points the light pen at
one of the previously displayed items at the top of the screen.
The old item disappears and is replaced by the new item.
Note that it is possible to display any item anywhere, and even
possible to display one item four times at the top.  Anyway,
the parameters mean the following.  Height is the height in
feet above the surface (terrain) of the moon.  It is the "radar"
height.  Altitude is the height above the "mean" height of the
moon ( I guess you would call it "mare" level).  Thus altitude
is not affected by terrain.  Angle is the angle of the ship in
relationship to the vertical.  10 degrees, -70 degrees, etc.
Fuel left is the amount of fuel left in pounds.  Thrust is the
amount of thrust (pounds) currently being produced by the engine.
Weight is the current earth weight of the ship.  As fuel is
burned off, the acceleration will increase due to a lessening of
weight.  The horizontal velocity is the current horizontal speed
of the ship, in feet per second.  It is necessary to land at
under 10 fps horizontal, or else the ship will tip over.
Vertical velocity is the downward speed of the ship.  Try to
keep it under 30 for the first few landings, until you get
better.  A perfect landing is under 8 fps.  The horizontal
and vertical accelerations are just those, in f/sec/sec.
With no power, the vertical acceleration is about 5 fp/s/s
down (-5).  Distance is the horizontal distance (X direction)
you are from the projected landing site.  Try to stay within
500 feet of this distance, because there are not too many
spots suitable for landing on the moon.  Seconds is just the
time since you started trying to land.  Thus you now know how
to display information and what they mean.

To control the ship, two controls are provided.  The first
controls the rolling or turning of the ship.  This is accom-
plished by four arrows just above the display menu.  Two point
left and two point right.  The two pointing left mean rotate
left and the two pointing right mean rotate right.  There is
a big and a little one in each direction.  The big one means
to rotate "fast" and the small one means to rotate "slow".
Thus to rotate fast left, you point the light pen at
left arrow.  To rotate slow right, you point the light pen at
the small arrow pointing to the right.  The arrow will get
slightly brighter to indicate you have chosen it.  Above the
arrow there is a bright, solid bar.  This bar is your throttle
bar.  To its left there is a number in percent (say 50%).  This
number indicates the percentage of full thrust your rocket
engine is developing.  The engine can develop anywhere from
10% to 100% thrust - full thrust is 10,500 pounds.  The
engine thrust cannot fall below 10%.  That is the way Grumman
built it (actually the subcontractor).  To increase or decrease
your thrust, you merely slide the light pen up and down the bar.
The indicated percentage thrust will change accordingly.

Now we come to actually flying the beast.  The module appears
in the upper left hand corner of the screen and is traveling
down and to the right.  Your job is to land at the correct
spot (for the time being, we will say this is when the
distance and height both reach zero).  The first picture you
see, with the module in the upper left hand corner, is not
drawn to scale (the module appears too big in relationship
to the mountains).  Should you successfully get below around
400 feet altitude, the view will now change to a closeup
view of the landing site, and everything will be in scale.
Remember, it is not easy to land the first few times, but
don't be disappointed, you'll do it.  Be careful, the game
is extremely addictive.  It is also quite dynamic.

Incorporated in the game are just about everything the GT40
can do.  Letters, italics, light pen letters, a light bar,
dynamic motion, various line types and intensities (the moon
is not all the same brightness you know).  It also shows that
the GT40 can do a lot of calculations while maintaining a
reasonable display.

There are three possible landing sites on the Moon:

    1.  On the extreme left of the landscape

    2.  A small flat area to the right of the mountains

    3.  In the large "flat" area on the right

Good Luck!
