.about {
    font-family: 'Helvetica Neue', sans-serif;
}
.about-content {
    line-height: 30px;
}
.about-top{
    width: 40%;
    margin: 50px auto 0 auto;
}
.about-content h1 {
    font-size: 32px;
    margin-bottom: 3rem;
}
.about-content h2 {
    font-size: 24px;
    margin-bottom: 3rem;
}
.about-content h3 {
    font-size: 16px;
    margin-bottom: 2rem;
}
.about-content p {
    margin-bottom: 2rem;
    font-weight: 500;
}
.about-bottom {
    border-top-width: 1px;
}
.about-history {
    width: 40%;
    margin: 0 auto;
    font-weight: 500;
}
.about-history-tile {
    display: flex;
    font-size: 20px;
    height: 120px;
    width: 100%;
    margin: 0 auto;
}

.history-title {
    text-align: center;
    font-size: 32px;
    font-weight: 600;
    margin: 100px 0;
}


.about-history {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    margin-bottom: 100px;
}

.history-line {
    position: absolute;
    left: 40%;
    top: 7%;
    transform: translateX(-50%) scaleY(0);
    /* 初期は見えない */
    transform-origin: top;
    /* 上から下に伸ばす */
    width: 4px;
    height: 90%;
    background-color: #222;
}

.history-item {
    display: flex;
    justify-content: space-between;
    width: 100%;
    margin: 50px 0;
}

.year {
    width: 40%;
    text-align: center;
    font-weight: bold;
}

.event {
    width: 50%;
    text-align: left;
}

.dot-a {
    position: absolute;
    top: 7%;
    left: 40%;
    transform: translate(-50%, -50%) scale(0);
    width: 14px;
    height: 14px;
    background-color: #222;
    border-radius: 50%;
    opacity: 0;
}
.dot-b {
    position: absolute;
    top: 32%;
    left: 40%;
    transform: translate(-50%, -50%) scale(0);
    width: 14px;
    height: 14px;
    background-color: #222;
    border-radius: 50%;
    opacity: 0;
}
.dot-c {
    position: absolute;
    top: 57%;
    left: 40%;
    transform: translate(-50%, -50%) scale(0);
    width: 14px;
    height: 14px;
    background-color: #222;
    border-radius: 50%;
    opacity: 0;
}
.dot-d {
    position: absolute;
    top: 82%;
    left: 40%;
    transform: translate(-50%, -50%) scale(0);
    width: 14px;
    height: 14px;
    background-color: #222;
    border-radius: 50%;
    opacity: 0;
}

@media screen and (max-width: 1350px) {
    .about-top {
        width: 60%;
    }
    .about-history {
        width: 60%;
    }
}
@media screen and (max-width: 600px) {
    .about-history {
        width: 80%;
    }
    .about-history-tile {
        font-size: 16px;
    }
}