Kingdom

©️ 2019 kwoolter 🐒

About

Python version of the old BBC Micro game 'Yellow River Kingdom' (aka 'Kingdom') that came on the Welcome cassette and was written by these legends in 1981:-

• Tom Hartley
• Jerry Temple-Fry
• Richard G Warner

Intro

• Written in python 3
• Run python run.py to start the command line interface
• Type start to get going
• Type play to start your next turn
• Keep typing play to start your next turn

Python Version

Classic Version

The Classic version uses the model-view-controller paradigm to structure the application as follows:-

• Model - main game logic for the Kingdom, each season and the map
• View - draw the status screens and the map using colorama module to add colours
• Controller - process user input and control the view and model accordingly

There is also an event queue for the model to pass events to the control for processing.

Remastered Content

The remastered content uses a stats engine to calculate if new events have been triggered based on the current status of the game.
The StatEngine class provides a framework for creating core stats and stats that are derived from core stats or from other derived stats. Whenever a stat changes all other stats that are dependent on the changed stat are automatically told to recalculate and are up to date in real-time. The remastered content in game-stats.py is essentially a bunch of calculations to see if an event triggers and what the impact of the event is.
New events can be easily added, are easy to tweak and don't impact the rest of the game logic. The StatEngine class is also used here (https://github.com/kwoolter/TRPGFramework) to track player stats in a text based adventure game. A java version is used here (https://github.com/kwoolter/DnDCharacterGen) to calculate DnD stats. This is a different approach to the Classic implementation which uses rules based code in the Season.calculate() method.

BBC Micro Version

You can play the original "Yellow River Kingdom" here:-

(http://bbcmicro.co.uk//index.php)

To get the game rules and calculations I looked at the BBC Basic source code by quitting the game and using the LIST command to pick my way through it.

Subsequently I found the source code here:-

(http://brandy.matrixnetwork.co.uk/examples/KINGDOM)

Code

The original code is very compact, has virtually no comments, uses short variable names and a lot of GOTO flow control.

Here is an example procedure that shows the logic used to calculate how much rice was planted and harvested each season (G) and how many people died from starvation (ST):

 6000 DEF PROCCALCULATE
 6010 IF B=0 THEN G=0:GOTO6100
 6020 ON S GOTO 6100,6030,6050
 6030 IF G>1000 THEN G=1000
 6040 G=G*(B-10)/B:GOTO6100
 6050 IF G<0 THEN 6100
 6060 G=18*(11+RND(3))*(0.05-1/B)*G
 6070 IF G<0 THEN 6100
 6080 F=F+INT(G)
 6100 ST=0:P=A+B+C:IF P=0 THEN 6299
 6110 T=F/P:IF T>5 THEN T=4:GOTO6200
 6120 IF T<2 THEN P=0:GOTO6299
 6130 IF T>4 THEN T=3.5:GOTO6200
 6140 ST=INT(P*(7-T)/7):T=3
 6200 P=P-ST:F=INT(F-P*T-ST*T/2)
 6210 IF F<0 THEN F=0
 6299 ENDPROC

Here is the code to calculate how many people the thieves killed (TD) and how much rice they stole (TF):

 5400 ON S GOTO 5410,5420,5430
 5410 I=200+RND(70)-C:GOTO5440
 5420 I=30+RND(200)-C:GOTO5440
 5430 I=RND(400)-C
 5440 I=INT(I):IF I<0 THEN I=0
 5450 TD=INT(C*I/400):C=C-TD
 5460 TF=INT(I*F/729+RND(2000-C)/10):IF TF<0 THEN TF=0
 5470 IF TF>2000 THEN TF=1900+RND(200)
 5480 F=F-TF
 5499 ENDPROC

Here is the code to calculate how many people were killed in the flood (FD), how much stored rice was lost (FF) and how much planted rice was lost (G).

 5790 VF=FL(1)+FL(2)+FL(3)
 5800 OP=A+B+C
 5810 A=INT((A/10)*(10-FS))
 5820 B=INT((B/10)*(10-FS))
 5830 C=INT((C/6)*(6-VF))
 5840 FF=INT(F*VF/6):F=F-FF
 5850 FD=OP-A-B-C
 5860 IF S=2 THEN G=G*(20-FS)/20
 5870 IF S=3 THEN G=G*(10-FS)/10
 5899 ENDPROC

If you want to delve deeper into the BBC Basic Code here are some helpers.

Variables

Variable	Purpose
P	Population
F	Stored Food Supplies
S	Current Season
Y	Current Year
A	People to defend the dyke
B	People to work in the fields
C	People to defend the villages
G	Baskets of rice to be planted in the fields
FD	Flood deaths
TD	Thief attack deaths
ST	Starvation deaths
FF	Stored food lost if floods
TF	Stored food taken by thieves
VF	Villages caught in the floods

Procedures

Procedure	Line	Purpose
DEF PROCNEWSEASON	3000	Start a new season
DEF PROCATTACK	5000	Thief attack logic
DEF PROCFLOOD	5500	Flood logic
DEF PROCCALCULATE	6000	Season end logic