Lunar Lander Game for the HP-65

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The program presented below will simulate a lunar lander on the HP-65. It was written by R. Scott (I don't have his first name!) and appeared in the V2N3P34 issue of PPC Journal (March 1975). Thanks to him wherever he is today!

You start out at an altitude of 10,000 feet and begin falling at the rate of 16 feet/second^2. You may decide to coast down for a period of time or burn fuel for a period of time. If you coast, your velocity increases at the rate of 16 feet/second^2. If you burn fuel, you decelerate at the rate of 32 feet/second^2. You are to land by having your velocity below 2 feet/second and your altitude at 2 feet above the moon or less.

The problem is: you only have 20 seconds of fuel to burn, so use it wisely!

Note: If you think you are a professional, be sure to set flag 1 after initializing the game at step 2 by pressing f SF1.

Instructions:
1) Load the program into the calculator and change back to RUN mode.
2) Start the game by pressing A. The display will show 10000.000 2a) Set a starting speed and increase the difficulty, if desired, by pressing f SF1, then enter your starting descent speed and press A again.
3) If you decide to coast, enter the number of seconds and press C.
4) If you decide to burn your engines, enter the number of seconds and press B.
5) After each action, the display will show your ALT.SPEED.
6) Repeat steps 3 and 4 until you land or crash.
7) A flashing display indicates either no fuel left or you have crashed (altitude < -2 and speed too high!)
8) If the landing is successful, the display shifts to an integer indicating your speed when you landed.
9) At any time, you may see how much fuel remains by pressing R/S. Then to return to ALT.SPEED, press R/S again. (Don't keep pressing R/S, however, as this will move you on into other parts of the program).

Program Listing: Email if you have any questions.
```Line      Instruction  Keycode
01         DSP          21
02         .            83
03         3            03
04         RCL 6        34 06
05         g            35
06         PI           02
07         +            61
08         ENTER        41
09         *            71
10         f-1          32
11         INT          83
12         f-1          32
13         TF1          61
14         0            00
15         g NOP        35 01
16         STO 6        33 06
17         EEX          43
18         2            02
19         *            71
20         STO 2        33 02
21         2            02
22         0            00
23         /            81
24         g LSTx       35 00
25         +            61
26         STO 8        33 08
27         EEX          43
28         4            04
29         STO 1        33 01
30         LBL          23
31         1            01
32         RCL 1        34 01
33         f            31
34         INT          83
35         RCL 2        34 02
36         EEX          43
37         3            03
38         /            81
39         +            61
40         R/S          84
41         RCL 8        34 08
42         R/S          84
43         g RDN        35 08
44         RTN          24
45         LBL          23
46         B            12
47         STO 3        33 03
48         RCL 8        34 08
49         -            51
50         CHS          42
51         STO 8        33 08
52         0            00
53         g X > Y      35 24
54         /            81
55         g NOP        35 01
56         RCL 3        34 03
57         3            03
58         2            02
59         CHS          42
60         GTO          22
61         2            02
62         LBL          23
63         C            13
64         STO 3        33 03
65         1            01
66         6            06
67         LBL          23
68         2            02
69         *            71
70         RCL 2        34 02
71         +            61
72         STO 2        33 02
73         g LSTx       35 00
74         +            61
75         RCL 3        34 03
76         *            71
77         2            02
78         /            81
79         RCL 1        34 01
80         -            51
81         CHS          42
82         STO 1        33 01
83         2            02
84         CHS          42
85         g X > Y      35 24
86         0            00
87         /            81
88         CHS          42
89         g X < = Y    35 22
90         GTO          22
91         1            01
92         RCL 2        34 02
93         g X > Y      35 24
94         GTO          22
95         1            01
96         DSP          21
97         .            83
98         0            00
99         GTO          22
100        1            01
```

That's it!
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