6歳の息子に負けた、げきよわ対戦型オセロを作ってみました。
置ける場所を複数の中から選んだのちに、ランダムにひとつ選んでいるので、弱いのです。。
また一瞬でコマをおくので戸惑います。

let choice = 0;
let flipCount = 0;
let pass = false;
let roboCount = 0;
let rC = 0;
let timer=0;
let timerStart=false;
let board = [
  [0, 0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 1, 2, 0, 0, 0],
  [0, 0, 0, 2, 1, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0, 0]
];
let turn = 1;
let s = 50;
let col;
let row;
let kururi = 0;
let count = 60;
let white = 0;
let black = 0;
let shiro;
let kuro;

let maxCount = 0;
let button1, button2, button3, button4;
let possible = false;

function setup() {
  createCanvas(400, 400);
  shiro = createDiv("白の番です。");
  kuro = createDiv("黒の番です。");
  textSize(48);
  button1 = createButton("コンピューターと対戦");
  button2 = createButton("友人同士で対戦");
  button3 = createButton("スキップ");
  button4 = createButton("最初からやり直す");
  button1.position(100, 100);
  button2.position(100, 200);
  button1.mousePressed(mode1);
  button2.mousePressed(mode2);
  button3.mousePressed(skip);
  frameRate(6);
}

function draw() {
  background(0, 140, 0);
  if (choice == 0) {  //対戦を選択する前
    shiro.hide();
    kuro.hide();
    button3.hide();
    button4.hide();
  }
  if(timerStart){
   timer++; 
  }
  if (choice == 1 || choice == 2) {　//選択したとき
    button1.hide();
    button2.hide();
    button3.show();
    button4.show();

    if (turn == 1) {　　//白の番です
      kuro.hide();
      shiro.show();
    }
    if (turn == 2) {　//黒の番です
      kuro.show();
      shiro.hide();
    }

    for (let i = 0; i < 8; i++) {
      for (let j = 0; j < 8; j++) {
        line(j * 50, 0, j * 50, height);
        line(0, i * 50, width, i * 50);
        if (board[i][j] == 1) {
          fill(255);
          ellipse(i * 50 + 25, j * 50 + 25, 40, 40);
        }
        if (board[i][j] == 2) {
          fill(0);
          ellipse(i * 50 + 25, j * 50 + 25, 40, 40);
        }
      }
    }

    if (count == 0) {　//カウントが0になったら結果を表示
      result();
    }

    if (turn == 2 && choice == 1) {   //ターンが２（黒）で対戦ロボにした場合

      let countR = [];    //変更することができるrowの場所を保存する変数
      let countC = [];    //変更することができるcolの場所を保存する変数
      let rC = 0;   //選択可能な場所を保存していく変数
      for (let i = 0; i < 8; i++) {
        for (let j = 0; j < 8; j++) {
          if (getpos(i, j) == 0) {   //ボード上にコマが置いてないところで
            check(i, j);   //チェック関数で置けるかをチェックしていく
            if (flipCount == 0) {   // 駒が一つも変わらないところは
              board[row][col] = 0;   //何も置かない
            } else {   //もし駒がひっくり返る場所の時
              rC++;//選択可能な場所の数を増やす
              countR[rC] = row;　  //変更することができるrowの場所を保存する
              countC[rC] = col;    //変更することができるcolの場所を保存する
              board[countR[rC]][countC[rC]] = 0;//いったん駒は消しておく
              print(countR[1], countC[1]);
            }
            if(rC==0){ //置く場所が無ければスキップ
              turn = 1;
            }
            
          }
        }
      }

      let choice=int(random(1,rC));    //選択可能な場所からランダムに一つ選ぶ    
      reverseC(countR[choice], countC[choice]);//ひっくり返す。
    }
  }
}

function reverseC(ro, co) {
  board[ro][co] = 2;
  for (let i = -1; i < 2; i++) {
    for (let j = -1; j < 2; j++) {
        serachReverse(ro, co, i, j);
    }
  }
  count--;
  turn = 1;
}

function check(r, c) {
  row = r;
  col = c;
  kururi = 0;
  flipCount = 0;
  board[row][col] = 2;
  for (let i = -1; i < 2; i++) {
    for (let j = -1; j < 2; j++) {
      checkReverse(row, col, i, j);
    }
  }
}

function getpos(x, y) {
  let xin = x >= 0 && x < 8;
  let yin = y >= 0 && y < 8;
  if (xin && yin) {
    return board[x][y];
  } else {
    return 0;
  }
}

function setpos(x, y, num) {
  let xin = x >= 0 && x < 8;
  let yin = y >= 0 && y < 8;
  if (xin && yin) {
    board[x][y] = num;
  }
}

function serachReverse(x, y, vx, vy) {
  let state = getpos(x, y);
  let Opponent;
  if (state == 1) {
    Opponent = 2;
  } else {
    Opponent = 1;
  }
  let hit = false;
  let step = 0;
  let stepx = x + vx;
  let stepy = y + vy;
  while (!hit) {

    if (getpos(stepx, stepy) == 0) {
      hit = true;
    }

    if (getpos(stepx, stepy) == Opponent) {
      stepx += vx;
      stepy += vy;
      step++;
    }
    if (step == 0) {
      if (getpos(stepx, stepy) == state) {
        hit = true;
      }
    }
    if (step >= 1) {
      if (getpos(stepx, stepy) == state) {
        hit = true;
        kururi++;
        let fillx = stepx;
        let filly = stepy;
        for (let i = 0; i < step; i++) {
          fillx -= vx;
          filly -= vy;
          setpos(fillx, filly, state);
          flipCount++;
        }
      }
    }
  }
}

function checkReverse(x, y, vx, vy) {
  let state = getpos(x, y);
  let Opponent;
  if (state == 1) {
    Opponent = 2;
  } else {
    Opponent = 1;
  }
  let hit = false;
  let step = 0;
  let stepx = x + vx;
  let stepy = y + vy;
  while (!hit) {

    if (getpos(stepx, stepy) == 0) {
      hit = true;
    }

    if (getpos(stepx, stepy) == Opponent) {
      stepx += vx;
      stepy += vy;
      step++;
    }
    if (step == 0) {
      if (getpos(stepx, stepy) == state) {
        hit = true;
      }
    }
    if (step >= 1) {
      if (getpos(stepx, stepy) == state) {
        hit = true;
        kururi++;
        let fillx = stepx;
        let filly = stepy;
        for (let i = 0; i < step; i++) {
          // fillx -= vx;
          // filly -= vy;
          // setpos(fillx, filly, state);
          flipCount++;
        }
      }
    }
  }
}

function mousePressed() {
  row = floor(mouseX / s);
  col = floor(mouseY / s);
  rCount = 0;
  if (getpos(row, col) == 0) {
    if (turn == 1) {
      kururi = 0;
      board[row][col] = 1;
      flipCount = 0;
      for (let i = -1; i < 2; i++) {
        for (let j = -1; j < 2; j++) {
          serachReverse(row, col, i, j);
        }
      }
      turn = 2;
      print("白がひっくり返した数:" + flipCount);
      if (kururi == 0) {
        board[row][col] = 0;
        turn = 1;
        count++;
      }
      count--;
    } else if (turn == 2 && choice == 2) {
      kururi = 0;
      flipCount = 0;
      board[row][col] = 2;

      for (let i = -1; i < 2; i++) {
        for (let j = -1; j < 2; j++) {
          serachReverse(row, col, i, j);
        }
      }
      turn = 1;
      print("黒がひっくり返した数:" + flipCount);
      if (kururi == 0) {
        board[row][col] = 0;
        turn = 2;
        count++;
      }
      count--;
    }
  }
}

function result() {
  for (let i = 0; i < 8; i++) {
    for (let j = 0; j < 8; j++) {
      let c = getpos(i, j);
      if (c == 1) {
        white++;
      } else if (c == 2) {
        black++;
      }
    }
  }
  if (white > black) {
    fill(255, 0, 0);
    text("white Win!", 100, 200);
  } else {
    fill(255, 0, 0);
    text("Black Win!", 100, 200);
  }
}

function keyPressed() {
  if (key == 's') {
    turn++;
    if (turn > 2) {
      turn = 1;
    }
  }
}

function mode1() {
  choice = 1;
}

function mode2() {
  choice = 2;
}

function skip(){
   turn++;
    if (turn > 2) {
      turn = 1;
    }
}