Arduino KY-027 Magic Light Cup Module is a set of two boards, each one has a led and a mercury tilt switch. Using PWM to drive the LEDs on each module you can achieve the effect of light being "magically" transferred from one module to the other when tilting them.

The KY-027 is a pair of modules, each one consist of a mercury switch, a led and a 10 kΩ resistor. Each board have a pins to control the switch, LED, power and ground.

Connect each module using the following diagram.

In this Arduino sketch we'll use both KY-027 modules to create the magic light cup effect. The mercury switches in each module provide a digital signal that is used to regulate the brightness of the LEDs using using PWM. Tilting the modules will decrease the brightness on one module while increasing it on the other one, creating the illusion of light magically passing from one module to the other.

int ledPinA = 9;
int switchPinA = 8;
int switchStateA = 0;
int ledPinB = 6;
int switchPinB = 7;
int switchStateB = 0;
int brightness   = 0;

void setup() 
{
  pinMode(ledPinA, OUTPUT); 
  pinMode(ledPinB, OUTPUT);  
  pinMode(switchPinA, INPUT); 
  pinMode(switchPinB, INPUT);
}

void loop() 
{
  switchStateA = digitalRead(switchPinA);
  if (switchStateA == HIGH && brightness != 255)
  { 
   brightness ++;
  } 
  switchStateB = digitalRead(switchPinB);
  if (switchStateB == HIGH && brightness != 0)
  { 
   brightness --;
  } 
  analogWrite(ledPinA, brightness);  //  A slow fade out
  analogWrite(ledPinB, 255 - brightness);  // B slow bright up
  delay(20);
}