it works

readme.md

@@ -50,3 +50,5 @@ https://github.com/empathicqubit/vscode-cc65-debugger/tree/master/src/__tests__/
 https://archive.org/details/The_Graphics_Book_for_the_Commodore_64/page/n25/mode/2up
 
 http://www.appleoldies.ca/cc65/docs/shr/shrworld.pd
+
+https://archive.org/details/The_Graphics_Book_for_the_Commodore_64/page/n59

src/main.c

@@ -13,18 +13,17 @@
 
 
 unsigned short i;
-unsigned short x; // maybe if the ant does not go tooo far it could be an int..
-BYTE y;
-BYTE direction; // 0 = right, 64 = up, 128 = left, 192 = down
-void setAndClearHiRes(void) {
-    // Hi-res is turned on by setting bits 5 and 6 (bit 6 must be set in any event) 
-    // of register 17 of the VIC and clearing bit 4 of register 22. 
-
-    
+short x; // maybe if the ant does not go tooo far it could be an int..
+short y;
+short direction; // 0 = right, 64 = up, 128 = left, 192 = down
+void setHiRes(void) {
     *(BYTE*)0xd011 = *(BYTE*)0xd011 | 0xb0 ; // Graphics on
     *(BYTE*)0xd016 = *(BYTE*)0xd016 & 240; //Multi color off
     *(BYTE*)0xd018 = *(BYTE*)0xd018 | 8 ; // Graphics to $2000
-
+}
+void clearHiRes(void) {
+    // Hi-res is turned on by setting bits 5 and 6 (bit 6 must be set in any event) 
+    // of register 17 of the VIC and clearing bit 4 of register 22. 
     // Clear memory
     for (i =0;i< 8000; i++)
     {
@@ -34,84 +33,116 @@ void setAndClearHiRes(void) {
     // Clear colors 
     for (i =0;i< 1000; i++)
     {
-        *(BYTE*)(0x400+i) = 0xF0; 
+        *(BYTE*)(0x400+i) = 0xf0; 
     }
 }
 
-int power2(int exponent)
+void fillHiRes(void) {
+    // Hi-res is turned on by setting bits 5 and 6 (bit 6 must be set in any event) 
+    // of register 17 of the VIC and clearing bit 4 of register 22. 
+    // Clear memory
+    for (i =0;i< 8000; i++)
     {
-    int result=1;
-    for (exponent; exponent>0; exponent--)
-    {
-        result = result * 2;
+        *(BYTE*)(0x2000+i) = 0xff; 
     }
-    return result;
+}
+
+
+void setAndClearHiRes(){
+    setHiRes();
+    clearHiRes();
 }
 
 // need to think
-BYTE isPositionBlack(unsigned short x, BYTE y)
+BYTE isPositionWhite(short x, short y)
 {
-    unsigned short ra = (320 * (BYTE)(y/8)) + (y & 7);
-    unsigned short ba = 8 * (BYTE)(x/8);
-    unsigned short ma = 255 - power2((7-(x & 7)));
-    unsigned short sa = 0x2000;
-    unsigned short ad = sa+ra+ba;
-    return 1;
-//    return *(BYTE*)(ad) & ma;
+    short ra = (320 * (short)(y/8)) + (y & 7);
+    short ba = 8 * (short)(x/8);
+    short ma = 1 << ((7-(x & 7)));
+    short sa = 0x2000;
+    short ad = sa+ra+ba;
+    return *(short*)(ad) & ma;
 }
 
 
 // https://archive.org/details/The_Graphics_Book_for_the_Commodore_64/page/n129/
-void setPositionWhite(unsigned short x, BYTE y)
+void setPositionWhite(short x, short y)
 {
-    unsigned short ra = (320 * (BYTE)(y/8)) + (y & 7);
-    unsigned short ba = 8 * (BYTE)(x/8);
-    unsigned short ma = power2((7-(x & 7)));
-    unsigned short sa = 0x2000;
-    unsigned short ad = sa+ra+ba;
-    *(unsigned short*)(ad) = *(unsigned short*)(ad) | ma;
+    short ra = (320 * (short)(y/8)) + (y & 7);
+    short ba = 8 * (short)(x/8);
+    short ma = 1 << ((7-(x & 7)));
+    short sa = 0x2000;
+    short ad = sa+ra+ba;
+    *(short*)(ad) = *(short*)(ad) | ma;
 }
 
-void setPositionBlack(unsigned short x, BYTE y)
+void setPositionBlack(unsigned short x, unsigned short y)
 {
-    unsigned short ra = (320 * (BYTE)(y/8)) + (y & 7);
-    unsigned short ba = 8 * (BYTE)(x/8);
-    unsigned short ma = 255 - power2((7-(x & 7)));
-    unsigned short sa = 0x2000;
-    unsigned short ad = sa+ra+ba;
-    *(unsigned short*)(ad) = *(unsigned short*)(ad) & ma;
-   
+    short ra = (320 * (short)(y/8)) + (y & 7);
+    short ba = 8 * (short)(x/8);
+    short ma = (1 << ((7-(x & 7))));
+    short sa = 0x2000;
+    short ad = sa+ra+ba;
+    *(short*)(ad) = (*(short*)(ad)) & ~ma;
 }
 
-void makeMove() {
-    if (isPositionBlack(x,y)) {
-        setPositionWhite(x,y);
-        direction = direction - 64;
-    } else {
-        setPositionBlack(x,y);
-        direction = direction + 64;
-    }
-}
-
-
-unsigned short line;
-int main(void) {
-    x = 160;
-    y = 100;
-    direction = 0;
-    setAndClearHiRes();
-
-    while(1)
-    {
+void moveForward() {
     if (direction == 0) {
         x = x+1;
     } else if (direction == 64) {
         y = y+1;
     } else if (direction == 128) {
         x = x-1;
-        } else {
+    } else if (direction == 192) {
         y = y-1;
     }
+}
+
+void turnLeft(){
+    direction = direction + 64;
+    if (direction >= 255) 
+        direction = 0;
+}
+
+void turnRight(){
+    direction = direction - 64;
+    if (direction <0) 
+        direction = 192;
+}
+
+
+void makeMove() {
+    if (isPositionWhite(x,y)) {
+        turnRight();
+        setPositionBlack(x,y);
+   } else {
+        turnLeft(); 
+        setPositionWhite(x,y);
+    }
+    moveForward();
+}
+
+unsigned short line;
+unsigned short foo; 
+unsigned short j; 
+int main(void) {
+
+    setAndClearHiRes();
+    for (i = 0;i<50;i++){
+        for (j= 0;j<50;j++){
+            setPositionWhite(i,j);
+        }
+    }
+     for (i = 0;i<50;i++){
+        for (j= 0;j<50;j++){
+            setPositionBlack(i,j);
+        }
+    }
+    x = 160;
+    y = 100;
+    direction = 0;
+    while(1)
+    {
        makeMove();
     }