// Spybotics Line Tracer
// Copyleft 2002 mac@research.co.jp

#define BUTTON	SENSOR_1
#define LIGHT	SENSOR_2
#define RIGHT	OUT_A
#define LEFT	OUT_B
#define LAMP	OUT_C

task main()
{
	int i;
	int black, white, th, sens;

	SetLight(LIGHT_ON);

	PlaySound(3);
	Wait(100);

	while(true) {
		PlayTone(LIGHT*10,10);
		Wait(10);
		if (BUTTON) break;
	}

	black = 0;
	for(i = 0; i < 128; i++) {
		black += LIGHT;
	}
	black /= 128;

	PlaySound(3);
	Wait(100);

	until(!BUTTON);
	while(true) {
		PlayTone(LIGHT*10,10);
		Wait(10);
		if (BUTTON) break;
	}

	white = 0;
	for(i = 0; i < 128; i++) {
		white += LIGHT;
	}
	white /= 128;

	th = (black + white) / 2;

	until(!BUTTON);

	while(true) {
		if (LIGHT < th) {
			Off(RIGHT);
			On(LEFT);
		}
		else {
			Off(LEFT);
			On(RIGHT);
		}
	}
}