Pumpkin Man: A (Simple) BASIC Game
Last week I showed how to create a Player (aka Sprite) in the shape of a pumpkin that you could move around the screen with the joystick.
The code was written in Atari BASIC and used an ML subroutine to actually move the player (well, actually it was two players side-by-side but moved together to look like on larger player).
This time, I have re-written the code using a better version of BASIC, which makes it much simpler to read and understand. Plus, it’s also faster.
In addition, I added a new feature where the pumpkin gets points by “eating candy” that is on the screen.
But first, the new version of last week’s program is below:
10 Rem PUMPKIN MAN
100 Graphics 18:Setcolor 2,0,0:Print #6;" HAPPY HALLOWEEN"
110 Pmgraphics 2
120 Pmclr 0:Pmclr 1
135 Pmcolor 0,2,8:Pmcolor 1,2,8
140 For I=P1+Y To P1+Y+13
150 Read D1
160 Poke I,D1
170 Next I
190 For I=P2+Y To P2+Y+13
200 Read D1
210 Poke I,D1
220 Next I
225 Set 7,1
260 If Hpos<20 Then Hpos=220
261 If Hpos>220 Then Hpos=20
270 Pmmove 0,Hpos;Vpos:Pmmove 1,Hpos+8;Vpos
280 Goto 240
5000 Rem PLAYER DATA
5010 Data 0,1,7,31,63,123,113,127,101,112,122,63,31,7
5020 Data 192,128,224,248,252,222,142,254,166,14,94,252,248,224
I wrote it using BASIC XE (but it also works in Altirra BASIC which also shares the same Player/Missile commands). Here’s a breakdown of the code:
Line 100: Switches to large-size character graphics mode and displays “HAPPY HALLOWEEN” on the screen.
Lines 110-220: Turn on Player/Missile Graphics, clear the memory area, set the player colors to orange, load the player data into the addresses for player 0 and 1.
Line 225: Allows the player to wrap between the top/bottom of the screen.
Lines 230-280:Moves the player based on how the joystick is moved.
Lines 5010-5020:Player data for the left and right parts of the pumpkin.
With that all working, the next thing is to display some “candy” on the screen and to get points when you “eat” it. For simplicity I will use the “c” character to indicate candy. Eventually I will want to redefine the character set with something more accurate, but this will work for now to get the concept across.
Since the game is run using Graphics 2, it already using big characters, so we can tell it to draw them to the screen using a subroutine:
4020 Position Xc,Yc:Print #6;"c"
We can call the subroutine in the initial setup:
235 GOSUB 4000
If you run the program now, you can still move the pumpkin around, but nothing happens to the candy. What we need to do is check the player for a collision with the playfield. The BASIC XE (and Altirra BASIC) command for that is BUMP. By using BUMP we can know when the player touches one of the characters (and thus “eats” it). We can then add a point to the score and remove the “candy” from the screen.
So first we can add another subroutine to erase the candy:
4100 Position Xc,Yc:Print #6;" "
And a routine to display the score:
4200 Position 0,11:Print #6;"SCORE:";Score
Now we can check to see if the pumpkin touches the candy by adding this to the main program loop:
275 If Bump(0,9)=1 Or Bump(1,9)=1 Then Gosub 4100:Gosub 4000:Hitclr :Score=Score+1:Gosub 4200
And lastly, display the score in the initialization:
235 Gosub 4000:Score=0:Gosub 4200
This is not the world’s most exciting game, but now when you move the pumpkin around and it touches the “C” for candy, the score will increase by 1 and candy will appear at a new position.
I really like BASIC XE as its extra commands help keep this code pretty easy to understand.
Future tasks for Pumpkin Man:
Add an enemy ghost that chases the pumpkin around the screen
Redefine the character set so that the “C” looks like an actual piece of candy.
Add some sound.
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Cool beans. Now, I'm tempted to return to BASIC.