# Snake.Bas

## Program: snake.bas

```basic
   1 REM ********************************************************************
   2 REM ZXSnake by Federico J. Alvarez Valero (2003-02-05)
  10 REM This program is free software; you can redistribute it and/or modify
  11 REM it under the terms of the GNU General Public License as published by
  12 REM the Free Software Foundation; either version 2 of the License, or
  13 REM (at your option) any later version.
  14 REM This program is distributed in the hope that it will be useful,
  15 REM but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 REM MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 REM GNU General Public License for more details.
  18 REM You should have received a copy of the GNU General Public License
  19 REM along with this program; if not, write to the Free Software
  20 REM Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  30 REM                   ENGLISH VERSION
  40 REM ********************************************************************

  50 BORDER 7 : PAPER 7 : INK 0 : CLS
  51 PRINT AT 3,13 ; PAPER 1 ; INK 7 ; "ZXSnake"
  52 PRINT AT 5,9 ; PAPER 7 ; INK 0 ; "Q - Up"
  53 PRINT AT 6,9 ; PAPER 7 ; INK 0 ; "A - Down"
  54 PRINT AT 7,9 ; PAPER 7 ; INK 0 ; "O - Left"
  55 PRINT AT 8,9 ; PAPER 7 ; INK 0 ; "P - Right"
  56 PRINT AT 10,3 ; PAPER 7 ; INK 0 ; "You have to pick up every"
  57 PRINT AT 11,3 ; PAPER 7 ; INK 0 ; "fruit on the screen while"
  58 PRINT AT 12,3 ; PAPER 7 ; INK 0 ; "growing up more and more..."
  59 PRINT AT 15,3 ; PAPER 7 ; INK 0 ; "Press any key to start"
  60 LET j$ = INKEY$
  61 IF j$ = "" THEN GOTO 60: END IF

  70 REM UDG
  71 DIM udg(1, 7) AS uByte => { {60, 66, 129, 129, 129, 129, 66, 60}, _
                                 {24, 60, 60, 60, 126, 251, 247, 126}}
  73 POKE UINTEGER 23675, @udg(0, 0): REM Sets UDG variable to point to the first element
  74 LET S$ = CHR$(144): LET F$ = CHR$(145)

  75 REM Variable declaration
  76 DIM p(23,34) AS UBYTE: REM Screen
  77 DIM x(23,34) AS UBYTE: REM Xorientations
  78 DIM y(23,34) AS UBYTE: REM Yorientations
  79 DIM c, f AS UBYTE
  80 DIM headx, heady AS UBYTE : REM Head coordinates
  81 DIM tailx, taily AS UBYTE : REM Tail coordinates
  90 DIM score, eaten as ULONG
  95 DIM maxx, maxy, minx, miny as UByte

 100 REM Variable definition
 110 LET headx = 11 : REM head x coordinate
 120 LET heady = 5 :  REM head y coordinate
 130 LET tailx = 5 :  REM tail x coordinate
 140 LET taily = 5 :  REM tail y coordinate
 150 LET orientationx = 1
 160 LET orientationy = 0

 165 REM Clear arrays p, x and y
 170 FOR c = 1 to 23: FOR f = 1 to 34
 180 LET p(c, f) = 0: LET x(c, f) = 0: LET y(c, f) = 0
 190 NEXT f: NEXT c

 200 LET score = 0
 210 LET eaten = 0
 220 LET maxx = 33
 230 LET maxy = 22
 240 LET minx = 0
 250 LET miny = 0

1000 REM Screen Initialization
1010 BORDER 1
1015 CLS
1020 PRINT AT 21,0 ; PAPER 1 ; INK 7 ; " SCORE :                       "
1030 FOR c = minx TO maxx
1040 LET p(miny+1,c+1) = 4
1050 LET p(maxy+1,c+1) = 4
1060 NEXT c
1070 FOR f = miny TO maxy
1080 LET p(f+1,minx+1) = 4
1090 LET p(f+1,maxx+1) = 4
1100 NEXT f

1500 GOSUB 8000 : REM Place first fruit

2000 REM Draw snake in its initial position
2001 PAPER 7 : INK 0
2005 REM Draw the body
2010 FOR c = tailx TO headx-1
2020 PRINT AT taily,c ; INK 0 ; "O"
2025 LET p(taily+2,c+2) = 3
2026 LET x(taily+2,c+2) = 1
2027 LET y(taily+2,c+2) = 0
2030 NEXT c
2040 REM Draw the Head
2050 PRINT AT heady,headx ; INK 0 ; S$;
2055 LET p(heady+2,headx+2) = 2
2056 LET x(heady+2,headx+2) = 1
2057 LET y(heady+2,headx+2) = 0

3000 REM Update snake position
3005 INK 0
3010 REM Change the orientation if needed
3015 LET x(heady+2,headx+2) = orientationx
3020 LET y(heady+2,headx+2) = orientationy
3025 REM Erase previous head
3030 PRINT AT heady,headx ; "O"
3035 LET p(heady+2,headx+2) = 3
3040 LET headx = headx + orientationx
3045 LET heady = heady + orientationy
3050 IF p(heady+2,headx+2) > 1 THEN GOTO 9900: END IF
3051 IF p(heady+2,headx+2) = 1 THEN
     LET score = score + 10 : PRINT AT 21,10 ; _
     PAPER 1 ; INK 7 ; score : LET eaten = 1 : GOSUB 8000: END IF
3055 REM Print the new head
3060 PRINT AT heady,headx ; S$;
3065 LET p(heady+2,headx+2) = 2
3070 IF eaten = 0 THEN GOSUB 8100: END IF
3080 LET eaten = 0

3200 REM Read the keyboard
3210 LET a$ = INKEY$
3220 IF orientationx < 1 AND (a$ = "O" OR a$ = "o") THEN
     LET orientationx = -1 : LET orientationy = 0: END IF

3230 IF orientationx > -1 AND (a$ = "P" OR a$ = "p") THEN
     LET orientationx = 1 : LET orientationy = 0: END IF

3240 IF orientationy < 1 AND (a$ = "Q" OR a$ = "q") THEN
     LET orientationx = 0 : LET orientationy = -1: END IF

3250 IF orientationy > -1 AND (a$ = "A" OR a$ = "a") THEN
     LET orientationx = 0 : LET orientationy = 1: END IF

3500 REM Pausa / Delay
3505 BEEP 0.005, 0
3510 FOR i = 1 TO 500:
     NEXT i

7998 GOTO 3000

8000 REM Fruit placement
8010 LET fruitx = INT(RND*30)+1
8020 LET fruity = INT(RND*20)+1
8030 IF p(fruity+2,fruitx+2) = 0 THEN GOTO 8050: END IF
8040 GOTO 8010
8050 PRINT AT fruity,fruitx ; INK 2 ; F$;
8060 LET p(fruity+2,fruitx+2) = 1
8070 RETURN

8100 REM Erase tail
8110 PRINT AT taily,tailx ; " "
8120 LET newtailx = tailx + x(taily+2,tailx+2)
8130 LET newtaily = taily + y(taily+2,tailx+2)
8140 LET p(taily+2,tailx+2) = 0
8150 LET x(taily+2,tailx+2) = 0
8160 LET y(taily+2,tailx+2) = 0
8170 LET tailx = newtailx
8180 LET taily = newtaily
8190 RETURN

9900 REM Game over
9910 PRINT AT 10,12 ; INK 2 ; "GAME OVER..."
9920 PRINT AT 11,10 ; INK 2 ; "SCORE : " ; score
9930 PRINT AT 13,10 ; INK 0 ; "Press any key"
9931 REM Mondatory pause so the msg. can be read
9932 FOR i = 0 TO 100

9933 NEXT i
9940 LET j$ = INKEY$
9950 IF j$ <> "" THEN GOTO 100: END IF
9960 GOTO 9940
```
