How does one add a random DELAY between 10 and 20 seconds?

For example in the following stepper logic I have a delay of 11 seconds - expressed in milliseconds as: delay(11000).

What would I need to add (or modify) so this is randomized between 10 and 20 seconds?

//#define IN1 8 //#define IN2 9 //#define IN3 10 //#define IN4 11

int Steps = 0; boolean Direction = true; unsigned long last_time; unsigned long currentMillis ; int steps_left=4095; long time;

void setup() { Serial.begin(115200); pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT); pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT);

} void loop() { while(steps_left>0){ currentMillis = micros(); if(currentMillis-last_time>=1000){ stepper(1); time=time+micros()-last_time; last_time=micros(); steps_left--; } } Serial.println(time); Serial.println("Wait...!"); delay(11000); // delay timing Direction=!Direction; steps_left=4095; }

Forgive the appearance of the code. Everytime I post it gets butchered. Hopefully it's understandable.

How does one add a random DELAY between 10 and 20 seconds?

For example in the following stepper logic I have a delay of 11 seconds - expressed in milliseconds as: delay(11000).

What would I need to add (or modify) so this is randomized between 10 and 20 seconds?

//#define IN1  8
//#define IN2  9
//#define IN3  10
//#define IN4  11

int Steps = 0;
boolean Direction = true;
unsigned long last_time;
unsigned long currentMillis ;
int steps_left=4095;
long time;

void setup()
{
Serial.begin(115200);
pinMode(IN1, OUTPUT); 
pinMode(IN2, OUTPUT); 
pinMode(IN3, OUTPUT); 
pinMode(IN4, OUTPUT); 


}
void loop()
{
  while(steps_left>0){
  currentMillis = micros();
  if(currentMillis-last_time>=1000){
  stepper(1); 
  time=time+micros()-last_time;
  last_time=micros();
  steps_left--;
  }
  }
   Serial.println(time);
  Serial.println("Wait...!");
  delay(11000);                     // delay timing
  Direction=!Direction;
  steps_left=4095;
}

Forgive the appearance of the code. Everytime I post it gets butchered. Hopefully it's understandable.