static void handle_key(int shift, int& value, int max)
static void handle_key(int shift, int& value, int max, int amt = 1)
static void handle_key(int shift, int& value, int max){	if(shift)		--value;	else		++value;	if(value<0)		value = max-1;	else if(value>=max)		value = 0;}