"Long Press" using LDRs

Hi, I am currently working on a project in witch I want to fire a laser at multiple LDRs (one at a time) to change the brightness of LEDs, I currently have my circuit working but need help adding an extra feature:

As it stands I shine a laser at my chosen LDR and an LED lights up with its set brightness, and extra LED also lights up, this can be ignored. I want to have it so that when I shine the laser at a specific LDR for 3 seconds, it locks that choice into place until I shine it at another LDR for 3 seconds. hope that makes sense, thanks in advance !!!

Here is the code so far:

const int LDR0 = A0;
const int LDR1 = A1;
const int LDR2 = A2;
const int LED = 9;
const int LED1 = 2;
const int threshold = 960;

void setup() {
  pinMode(LED, OUTPUT);
  pinMode(LED1, OUTPUT);

void loop() {
int LDR0_val = analogRead(LDR0);
  delay (50);
int LDR1_val = analogRead(LDR1);
  if (LDR0_val > threshold) {
 analogWrite(LED, 10);
 digitalWrite(LED1, HIGH);
  else if (LDR1_val > threshold) { 
    analogWrite(LED, 150);
  else {

This Thread has good code for different "keypress" times which can probably be adapted for your needs.