body {
    margin: 0;
    padding: 0;
    width:5000
    height:5000
    font-family: Arial;
    background-image: url('back_pic.jpg'); /* BODYの背景画像 */
    background-size: auto; /* または contain, autoなど */
    background-position: center;
    background-size: contain;
    background-attachment: fixed; 背景画像を固定
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    margin: 0;
    
    text-align: center;/*四則演算*/
    margin-top: 50px;
}

header, footer {
    /*padding: 20px;*/
    text-align: center;
    background-color: black; /*半透明の白背景 */
}

main{
	text-align: center;
    background-color: Transparent; 
}

/* デスクトップ向けのスタイル*/
@media (min-width: 1200px) {
    .container {
        width: 1200px;
        margin: 0 auto;
    }
}

/* タブレット向けのスタイル*/
@media (min-width: 768px) and (max-width: 1199px) {
    .container {
        width: 90%;
        margin: 0 auto;
    }
}

/* スマートフォン向けのスタイル*/
@media (max-width: 767px) {
    .container {
        width: 100%;
        margin: 0 auto;
    }
}

.container {
	margin: 0;
    padding: 0;
   width: 80%; 
   margin: 0 auto;
    background-color: Transparent;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

.container {
    /*display: flex;*/
    justify-content: space-between;
    align-items: center;
    padding: 10px;
}

.item {
    flex: 1;
    margin: 5px;
    text-align: center;
}

body {
    /*display: flex;*/
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: black;
    /*margin: 0;*/
    font-family: Arial;
}

.calculator {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    padding: 20px;
    width: 300px;
    top:0
    left:0
}

#display {
	top:100
	left:5000
    width: 100%;
    padding: 10px;
    font-size: 2em;
    text-align: right;
    margin-bottom: 10px;
    border: none;
    border-bottom: 2px solid blue;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

button {
    padding: 20px;
    font-size: 1.5em;
    border: none;
    background-color: #f0f0f0;
    cursor: pointer;
    border-radius: 5px;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #ddd;
}

.image-container {
    width: 500px;
    height: 500px;
    overflow: hidden;
}

#rotatingImage {
    width: 100%;
    height: 100%;
    animation: rotateImage 5s linear infinite;
}

@keyframes rotateImage {
    from {
        transform: rotateY(0deg);
    }
    to {
        transform: rotateY(360deg);
    }
}

h1 {
    color: blue;
    font-size: 40px;
    float: left;
}

#counter {
    font-size: 100px;
    color: blue;
}

p {
    color: blue;
    font-size: 100px;
}
a {
     color: blue;
}

.px{
	font-size: 45px
}

.Sbox {
	 position: relative;
     top: -500px;
     left: calc(100% - 500px);
     width: 400px;
     height:300px;
     background-color: transparent;
     border: 2px solid blue;
     font-size: 30px;
     opacity: 0.5;
}

/*.container {
      position: relative;
      width: 1000px;
      height: 2000px;
      background-color: transparent;
}*/

.iframe-container {
         position: relative;
         width: 100%;
         padding-bottom: 56.25%; 
         height: 0;
         overflow: hidden;
}
.iframe-container iframe {
         position: absolute;
         top: 0;
         left: 0;
         width: 100%;
         height: 100%;
         border: 0;
}

.image-container2 {
          opacity: 0;
          transform: translateY(100px);
          transition: opacity 1s ease-out, transform 1s ease-out;

}
.image-container.show {
           opacity: 1;
           transform: translateY(0);
}

.box {
            width: 600;
            max-width: 300px;
            height: 350px;
            overflow: hidden;
            border: 1px solid #000;
            display: flex;
            align-items: right;
            justify-content: center;
            font-size: 16px;
            transition: transform 0.5s ease;
}

.fullscreen {
            width: 100%;
            height: 100%;
            background-color: white;
}

.text-center {
    text-align: center;
}

#box {
            width: 400px;
            height: 200px;
            border: 3px solid blue;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 50px;
            transition: font-size 0.7s ease-in-out;
}

.main-content {
    width: 100%;
    padding: 20px;
    background-color: Transparent;
    box-sizing: border-box;
}

.footer {
      position: sticky;
      bottom: 0;
      width: 100%;
      background-color: Transparent;
      text-align: center;
      padding: 10px;
}

#image {
    transition: transform 0.3s ease;
}
.container {
    /*display: flex;*/
    flex-wrap: wrap;
}

.container img {
    margin: 0;
}

.small {
    transform: scale(0.5);
}

.large {
    transform: scale(1.2);
}

/* ベンダープレフィックスを使用したトランスフォーム */
.element {
    -webkit-transform: rotate(45deg); /* Chrome, Safari, iOS */
    -moz-transform: rotate(45deg);    /* Firefox */
    -ms-transform: rotate(45deg);     /* Internet Explorer, Edge */
    transform: rotate(45deg);         /* 標準プロパティ */
}

/* ベンダープレフィックスを使用したトランジション */
.element {
    -webkit-transition: all 0.5s ease; /* Chrome, Safari, iOS */
    -moz-transition: all 0.5s ease;    /* Firefox */
    -o-transition: all 0.5s ease;      /* Opera */
    transition: all 0.5s ease;         /* 標準プロパティ */
}

.footer-image {
    width: 100%;
    /* 画像の高さを最大幅に合わせる場合 */
    height: auto;
    /* または固定高さにする場合 */
    /* height: 300px; */
    object-fit: cover; /* 画像が歪まないように */
}


/*#clock {
            font-size: 2em;
            font-family: 'Arial';
            text-align: center;
            margin-top: 20%;
}*/
.clock {
    font-family: 'Arial';
    color: blue;
    font-size: 48px;
    text-align: center;
    padding: 20px;
    margin-top: 20%;
}


#stopwatch {
            font-size: 2em;
            margin-bottom: 20px;
        }
        button {
            font-size: 1em;
            margin: 5px;
}

#blinkingText {
    font-size: 1.5em;
    color: blue;
    text-align: center;
    /*margin-top: 20%;*/
}

input, select, button {
    font-size: 1em;
    margin: 5px;
}

<style>
.message-container {
            position: relative;
            height: 600px;
            background-color: white;
        }

        .message {
            position: absolute;
            top: 1000px; /* 初期位置を設定 */
            /*left: 600px;*/
            left: calc(100% - 750px);
            background-color: white;
            padding: 10px;
            border: 1px solid blue;
        }

        .move-up {
            top: 2400px; /* top位置を上げる（上に移動）問題 */
}
</style>

.image-container {
    width: 200px;
    height: 200px;
    position: absolute; /* 位置を絶対に設定 */
    background-color: lightblue;
    transition: transform 1s ease;
}

.image1 {
    top: 50px;
    left: 50px;
}

.image2 {
    top: 300px;
    left: 300px;
}