var any_var;  // type is Any
var number = 10; // type is Int
number = "123";  // valid

var number2 := 10; // specific type is Int
var number3: Int = 10; // both is ok
/* 
number2 = 3.14;
invalid!
*/

const Pi := 3.14; // recommended, auto detect type
// equal -> const Pi: Double = 3.14;