ESP8266 - webserver - Handleroot connections

//ESP8266 (NodeMCU) - webserver - handling Root connections
//Author: Martin Chlebovec
//Web: https://arduino.php5.sk?lang=en
//Donate: https://paypal.me/chlebovec
//Date: 9. Feb. 2020

#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
const char *ssid = "MY_WIFI";
const char *password = "MY_PASSWORD";
ESP8266WebServer server(80);

void handleRoot() {
  String response;
  response = "<!DOCTYPE html>\n";
  response += "<html>\n";
  response += "<head>\n";
  response += "<link rel=\"stylesheet\" type=\"text/css\" href=\"https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css\">\n";
  response += "<style>\n";
  response += "body {background-color: #F5B041;}\n";
  response += "</style>\n";
  response += "<title>Login V16</title>\n";
  response += "</head>\n";
  response += "<body>\n";
  response += "<center><button type=\"button\" class=\"btn btn-success\">OLA</button></center>\n";
  response += "</body>\n";
  response += "</html>";
  server.send(200, "text/html", response);
}

void setup() {
  Serial.begin(115200);
  delay(1000);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  Serial.println("");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println(".");
  }
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  server.on("/", handleRoot);
  server.begin();
}

void loop() {
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println(".");
  }
  server.handleClient();
}