// Frantick.cmm - silly CEnvi program to bounce an asterisk around the screen

// find out how big the screen is
MaxRow = ScreenSize().row - 1;
MaxCol = ScreenSize().col - 1;

// get a random initial position for the bouncy asterisk
srand();
OldRow = rand() % (MaxRow + 1);
OldCol = rand() % (MaxCol + 1);

// clear the screen to start with a fesh slate
ScreenClear();

while ( !kbhit() ) {
   // draw new dots and erase old ones forever
   do {
      // calculate new row, so long as it is in bounds
      Row = OldRow + (rand() % 3) - 1;
   } while( Row < 0  ||  MaxRow < Row );
   do {
      // calculate new column, so long as it is in bounds
      Col = OldCol + (rand() % 3) - 1;
   } while( Col < 0  ||  MaxCol < Col );
   SafePutchar(' ',OldRow,OldCol);
   SafePutchar('*',OldRow = Row,OldCol = Col);
}

SafePutchar(c,row,col) // just like putchar, but won't write into lower-right corner
{                      // so we don't get accidental scrolling
   ScreenCursor(col,row);
   if ( row != MaxRow  ||  col != MaxCol ) {
      putchar(c);
   }
   ScreenCursor(col,row);
}

// flush the keyboard
while( kbhit() ) getch();