关于reactjs的快速问题所以我是新的React，我试图使井字游戏的应用程序。
目前，这是我所拥有的：App.js：

import logo from './logo.svg';
import './App.css';
import { Row } from './components/Row';
import {Board} from './components/Board'
function App() {
  // App renders Row
  return (
    <div>
      <Board />
    </div>
    
  );
}
export default App;

Board.js

import React from "react";
import { ReactDOM } from "react";
import { Row } from "./Row";
export function Board() {
    return (
        <div className="Board">
            <Row />
            <Row />
            <Row />
        </div>
    )
}

Row.js

import React from 'react';
import ReactDOM from 'react-dom';
import { Square } from './Square';
export function Row() {
    return(
        <div className='Row'>
            <Square />
            <Square />
            <Square />
        </div>
    )
}

Square.js

import React, {useState} from 'react';
import ReactDOM from 'react-dom';
export function Square(props){
    // Square is rendered by App
    const [currLetter, changeLetter] = useState(" ");
    function toggleLetter(str) {
        if(str === " ") {return "X";}
        else if(str === "X") {return "O";}
        else if(str === "O") {return "X";}
    }
    return(
        <div >
            <button onClick={() => changeLetter(toggleLetter)} className='Square'> {currLetter} </button>
        
        </div>
               
    );
}

它运行得很好，但我想知道为什么当我这样写Square.js时它不起作用：

export function Square(props){
    // Square is rendered by App
    const [currLetter, changeLetter] = useState("X");
    function toggleLetter(str) {
        if(str === "X") {changeLetter("O");}
        else if(str === "O") {changeLetter("X");}
    }
    return(
        <div >
            <button onClick={toggleLetter} className='Square'> {currLetter} </button>
        
        </div>
               
    );
}

为什么onClick不能直接接收toggleLetter呢？这是一个函数，对吗？

第二个问题这是我的CSS看起来像：

.Board {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  
  /* width: 55%;
  height: 55%; */
  margin-top: 18%;
}
.Row {
  text-align: center;
  /* position: absolute; */
  /* left: 35%;
  right: 50%;
  top: 25%;
  
  width: 25%;
  height: 25%; */
  display: flex;
  flex-direction: row;
  justify-content: center;
  
}
.Square {
  /* position: absolute; */
  
  width: 70px;
  height: 70px;
  border-color: #99ccff;
  text-align: center;
  font-size: xx-large;
  font-family: 'Courier New', Courier, monospace;
}
/* .Row {
} */
.App-logo {
  height: 40vmin;
  pointer-events: none;
}
@media (prefers-reduced-motion: no-preference) {
  .App-logo {
    animation: App-logo-spin infinite 20s linear;
  }
}
.App-header {
  background-color: #282c34;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  font-size: calc(10px + 2vmin);
  color: white;
}
.App-link {
  color: #61dafb;
}
@keyframes App-logo-spin {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}
body {
  min-height: 100%;
  margin: 0;
  padding: 0;
  background-color: #ffcccc;
}
html {
  height: 100%;
}

我想做的是确保板子以身体为中心，因此以页面为中心。因为它是，它是在页面上的中心，但随后身体被移下。当我检查页面时，主体的顶部边缘被向下移动到与板的顶部边缘相同的水平，而不是主体在默认情况下的位置，而板在其中心。我该怎么解决？
它看起来像什么：
how-it's-going