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!