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Simple game movement code
Post by Falan on Nov 29th, 2015, 8:37pm

Hi there I wonder if there are any examples of basic coding that I could use to make a character move around the screen and perhaps animate some enemies?

I have worked through the tutorials in BBC BASIC but I am having difficulty finding code for movements.

I want to have a simple screen that I can move around in and maybe interact with other things there. Possibly have enemies moving about to avoid, the usual things.

If there are any examples of this I would really appreciate any help finding them thanks smiley
Re: Simple game movement code
Post by Richey on Nov 30th, 2015, 02:11am

Hello Falan

in the first instance I would suggest referring firstly to Chapter 13 of the tutorial for information on using INKEY.

http://bbcbasic.co.uk/bbcwin/tutorial/chapter13.html

Then it's probably worth reading from there to chapter 19.

Hope this helps.

Best wishes.
Re: Simple game movement code
Post by Falan on Nov 30th, 2015, 05:14am

Many thanks I will continue from Chapter 13 then thanks smiley

Edit- Ok thanks I read through those tutorials and I have looked at some game code. I cannot find anything simple enough to break down into chunks I can make sense of though.

I was hoping to draw a small window and then move a character (I already made some) around the screen. I think the 'space invaders' demo was close because it drew the window and gave control over the character left and right and also deleted the old character each time it moved.

It was frustrating though because there was a lot of other stuff going on. I would like to link up the movement on the screen to trigger a text based adventure script. I will keep searching but if anyone knows any real simple movement code I can adapt I would love to see it thanks.
Re: Simple game movement code
Post by DDRM on Dec 1st, 2015, 5:14pm

Hi Falan,

OK, sounds like the text-based graphics in the tutorial are a good starting place for what you want. Is this too simple to be useful?

Code:
      REM Set up a 640 x 512 pixel window and clear it to black
      REM This mode gives us 80 characters wide and 32 deep
      MODE 8
      REM Set up player's initial position, in characters
      playerx%=40
      playery%=16
      REPEAT
        PRINT TAB(playerx%,playery%)," "  :REM Clear out last position
        t$=INKEY$(0)   :REM check keyboard for instructions to move player
        CASE t$ OF
          WHEN "z","Z":playerx%-=1
          WHEN "x","X":playerx%+=1
          WHEN "a","A":playery%+=1
          WHEN "q","Q":playery%-=1
        ENDCASE
        PRINT TAB(playerx%,playery%),"O"   :REM Draw player in new position
        WAIT 5      :REM Wait a while (partly to give your processor a rest!)
      UNTIL  playerx%<0 OR playerx%>79 OR playery%<0 OR playery%>31

By adding code to show your enemies, or the landscape, you could make it more interesting. By detecting (as shown in the tutorial using GET(x,y) you should be able to trigger a branch to the event in your text-based story.

Later you will probably want to use the graphics functions. In particular, you might want to look at using VDU 5 to tie text to the graphics cursor (which you can move with MOVE) to get finer control. Then you can use POINT to look at the colour of the screen there.

Hope that's useful,

D
Re: Simple game movement code
Post by KenDown on Dec 7th, 2015, 6:50pm

There are two methods to move things around the screen. The first uses the fact that if you EOR a number twice you get the original number.
PRINT10EOR128 which gives you 138
PRINT138EOR128 gives you 10 again

GCOL3,9
x%=100
REPEAT
CIRCLEFILLx%,100,20
g%=GET
CIRCLEFILLx%,100,20
IFg%=137x%+=2
UNTILx%=1400

Press the right arrow key and the blue circle will move to the right. This works very nicely - until you start putting background in and then, because the circle is "painted" onto the screen, you will get funny results. Try putting a solid rectangle in the way of the circle to see what I mean.

(Incidentally, in immediate mode - click on the keyboard symbol in your BB4W window - type
PRINTGET
then press the left arrow key. That will give you the code for which you should test to get your circle moving left. Do the same (and adapt the program) to get the circle moving up and down.

As someone else has already pointed out, GET or INKEY(0) is a fairly slow way of getting user input. Using INKEY with a negative number (look up "INKEY" in the help supplied with BB4W) will be much faster - maybe even too fast!

The other method is to use sprites, but I won't tell you about that. It's far too complicated and is so clearly explained in the Help files that even I can understand it.

Hope this helps.