#include <exec/types.h>
#include <hardware/custom.h>

extern struct Custom custom;
/*
 * declare memory mapped chip areas as volatile to ensure
 * the compiler does not optimize away the access.
 */
volatile UBYTE *ciaa_pra = (volatile UBYTE *) 0xbfe001;
volatile UBYTE *custom_vhposr= (volatile UBYTE *) 0xdff006;
#define PRA_FIR0_BIT    (1 << 6)
#define COLOR_WHITE     (0xfff)
#define COLOR_WBENCH_BG (0x05a)
#define TOP_POS         (0x40)
#define BOTTOM_POS      (0xf0)

int main(int argc, char **argv)
{
    UBYTE pra_value = 0;
    UBYTE pos = 0xac;
    BYTE incr = 1;

    while ((*ciaa_pra & PRA_FIR0_BIT) != 0) {
        while (*custom_vhposr != 0xff) ; // wait for vblank
        while (*custom_vhposr != pos) ;  // wait until position reached
        custom.color[0] = COLOR_WHITE;
        while (*custom_vhposr == pos) ;  // wait while on the target position
        custom.color[0] = COLOR_WBENCH_BG;
        if (pos >= 0xf0) incr = -incr;
        else if (pos <= 0x40) incr = -incr;
        pos += incr;
    }
    return 0;
}