{

    initialize();

    ($alt,$speed) = sensors();
    while ($alt > 400) {
	firethrusters(1);
	($alt,$speed) = sensors();
    }

    $goalspeed = -1;

    $currentthrust = 3;
    while (!landed()) {
	($prevalt,$prevspeed) = sensors();

	firethrusters($currentthrust);

	($alt,$speed) = sensors();

	if ($speed < $goalspeed) {
	    $currentthrust += 1;
	} elsif ($speed > 0) {
	    $currentthrust = 2;
	    firethrusters(0);
	} else {
	    $currentthrust--;
	}
    }

    cleanup();
}