Build a Spring Festival Magic Calculator in Go – Step‑by‑Step Tutorial

Magic Principle

The trick uses the identity C = T - (A + B), where T is a predetermined target number, and A and B are numbers supplied by the audience. By construction A + B + C = T, so the sum always equals the target.

Set target time T
Audience provides A and B
C = T - (A + B)
// Then A + B + C = T

In the example the target T is 2162227, representing the date‑time 02‑16 22:27.

Go Implementation

A MagicCalculator struct stores the numeric target and its human‑readable timestamp.

// MagicCalculator magic calculator
type MagicCalculator struct {
    targetTime int   // numeric target time
    timestamp  string // formatted time string
}

The constructor builds the target from the current date and time, formatting month, day, hour and minute into a string like 2162227 and converting it to an integer.

func NewMagicCalculator() *MagicCalculator {
    now := time.Now()
    month := int(now.Month())
    day := now.Day()
    hour := now.Hour()
    minute := now.Minute()
    timestamp := fmt.Sprintf("%d%02d%02d%02d", month, day, hour, minute)
    target, _ := strconv.ParseInt(timestamp, 10, 64)
    return &MagicCalculator{targetTime: int(target), timestamp: timestamp}
}

The method GetMagicNumber implements the core formula.

func (mc *MagicCalculator) GetMagicNumber(num1, num2 int) int {
    return mc.targetTime - (num1 + num2)
}

An interactive routine reads two numbers from the user, computes the magic number, verifies the sum, and prints the corresponding timestamp.

func InteractiveMagic() {
    fmt.Println("=== Interactive Magic Experience ===")
    fmt.Println("Enter two numbers and watch the trick unfold")
    mc := NewMagicCalculator()
    var num1, num2 int
    fmt.Print("Enter first number: ")
    fmt.Scan(&num1)
    fmt.Print("Enter second number: ")
    fmt.Scan(&num2)
    fmt.Printf("
You entered: %d and %d
", num1, num2)
    magicNum := mc.GetMagicNumber(num1, num2)
    fmt.Printf("Magic number (third number) is: %d
", magicNum)
    fmt.Printf("
Verification: %d + %d + %d = %d
", num1, num2, magicNum, mc.targetTime)
    fmt.Printf("This number represents the time: %s
", mc.timestamp)
}

The program entry point simply calls the interactive function.

func main() {
    InteractiveMagic()
}

Running the Program

When executed and the audience numbers 1106 and 88396 are entered, the program outputs a magic number 2081398. The verification line shows 1106 + 88396 + 2081398 = 2170900, which corresponds to the date‑time 02‑17 09:00 (the moment the program was run).

Source Code

Full source code is available at https://github.com/jianghushinian/blog-go-example/tree/main/2026-spring-festival-magic