OLED Whack-A-Mole Game

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_MCP23X17.h>
#include <esp_system.h>
TwoWire scoreBus(1);
Adafruit_SSD1306 game(128,64,&Wire,-1), points(128,64,&scoreBus,-1);
Adafruit_MCP23X17 io;
const uint8_t leds[]={4,13,14,16,17,18,19,23,25};
const uint8_t keys[]={0,1,2,3,4,5,6,8,9,10};
struct Button { bool raw=false,down=false; uint32_t changed=0; } buttons[10];
enum State {READY,COUNT,PLAY,OVER};
State state=READY;
uint32_t phaseAt=0,playAt=0,moleAt=0;
int countdown=3,score=0,target=-1,lastSeconds=-1;
bool dirty=true,scoreDirty=true;
void lightsOff(){for(auto p:leds)digitalWrite(p,LOW);target=-1;}
void nextMole(uint32_t now){int old=target;lightsOff();do {target=esp_random()%9;}while(target==old);digitalWrite(leds[target],HIGH);moleAt=now;}
void render(int seconds){
 if(dirty){
  game.clearDisplay();game.setTextColor(SSD1306_WHITE);game.setCursor(0,0);
  if(state==READY){game.setTextSize(3);game.println("Start");game.setTextSize(1);game.println("Press START button");}
  else if(state==COUNT){game.setTextSize(4);if(countdown)game.print(countdown);else game.print("Go!");}
  else if(state==PLAY){game.setTextSize(2);game.println("Time left");game.setTextSize(3);game.print(seconds);game.setTextSize(1);game.println(" seconds");}
  else {game.setTextSize(2);game.println("Game Over");game.setTextSize(1);game.print("Score: ");game.println(score);game.println();game.println("Press START to replay");}
  game.display();dirty=false;
 }
 if(scoreDirty){points.clearDisplay();points.setTextColor(SSD1306_WHITE);points.setCursor(0,0);points.setTextSize(2);points.println("Score");points.setTextSize(3);points.println(score);points.display();scoreDirty=false;}
}
void setup(){
 Serial.begin(115200);
 for(auto p:leds){pinMode(p,OUTPUT);digitalWrite(p,LOW);}
 Wire.begin(21,22);scoreBus.begin(32,33);
 if(!io.begin_I2C(0x20,&Wire)||!game.begin(SSD1306_SWITCHCAPVCC,0x3C,true,false)||!points.begin(SSD1306_SWITCHCAPVCC,0x3C,true,false)){
  Serial.println("Initialization failed: check displays and expander wiring.");while(true)delay(100);
 }
 // A7 and B7 remain outputs: these pins must not be used as inputs.
 io.pinMode(7,OUTPUT);io.digitalWrite(7,LOW);io.pinMode(15,OUTPUT);io.digitalWrite(15,LOW);
 for(auto k:keys)io.pinMode(k,INPUT_PULLUP);
 render(30);
}
void loop(){
 uint32_t now=millis();bool pressed[10]={};uint16_t raw=io.readGPIOAB();
 for(int i=0;i<10;i++){
  bool down=!(raw&(1<<keys[i]));auto &b=buttons[i];
  if(down!=b.raw){b.raw=down;b.changed=now;}
  if(now-b.changed>=25 && b.down!=b.raw){b.down=b.raw;pressed[i]=b.down;}
 }
 if((state==READY||state==OVER)&&pressed[9]){score=0;scoreDirty=true;state=COUNT;countdown=3;phaseAt=now;dirty=true;lightsOff();}
 if(state==COUNT && now-phaseAt>=1000){phaseAt=now;if(countdown>0){countdown--;dirty=true;}else{state=PLAY;playAt=now;lastSeconds=-1;nextMole(now);dirty=true;}}
 int seconds=30;
 if(state==PLAY){
  uint32_t elapsed=now-playAt;
  if(elapsed>=30000){state=OVER;lightsOff();dirty=true;seconds=0;}
  else{
   seconds=(30000-elapsed+999)/1000;
   if(seconds!=lastSeconds){lastSeconds=seconds;dirty=true;}
   if(target>=0 && pressed[target]){score++;scoreDirty=true;nextMole(now);}
   else if(now-moleAt>=1000)nextMole(now);
  }
 }
 render(seconds);delay(2);
}