.a4-wrapper {
    width: 100%;
    display: flex;
    justify-content: space-between;
}

.a4-left {
    position: sticky;
    top: 90px;
    height: fit-content;
}

.a4-left h1 {
    color: #222;
    font-size: 55px;
    font-weight: 800;
}

.a4-left p {
    color: #888;
    font-size: 18px;
    font-weight: 300;
    line-height: 1.7;
    margin-top: 2rem;
}

.a4-left a {
    color: #555;
    width: fit-content;
    font-size: 16px;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 5px;
    margin-top: 4rem;
    transition: all .3s ease;
    animation: mobmob 1.2s infinite;
}

@keyframes mobmob {
    0% {
        gap: 5px;
    }
    10% {
        gap: 8px;
    }
    20% {
        gap: 5px;
    }
    30% {
        gap: 8px;
    }
    40% {
        gap: 5px;
    }
    100% {
        gap: 5px;
    }
}

.a4-box-wrapper {
    position: relative;
    width: 700px;
    display: flex;
    flex-direction: column;
    gap: 5rem;
}

.a4-vertical {
    position: absolute;
    top: 0; left: -80px;
    width: 1px;
    height: 100%;
    border-left: 1px dashed var(--main-color);
    opacity: .3;
}

.a4-box {
    position: relative;
}

.a4-box-num {
    position: absolute;
    top: 40%; left: -102px;
    transform: translate(0, -50%);
    width: 45px;
    height: 45px;
    color: #fff;
    font-size: 18px;
    font-weight: 300;
    letter-spacing: 0.02em;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 100%;
    background-color: var(--main-color);
    -webkit-animation: pulseAnim 1.3s infinite;
    animation: pulseAnim 1.3s infinite;
}

@keyframes pulseAnim {
	0% {
		box-shadow: 0 0 0 0 rgba(15, 155, 231, 30%);
	}
	70% {
		box-shadow: 0 0 0 15px rgb(151 213 229 / 0%);
	}
	100% {
		box-shadow: 0 0 0 0 rgb(151 213 229 / 0%);
	}
}

.a4-box-image img {
    width: 100%;
    object-fit: cover;
}

.a4-box-text {
    padding-top: 15px;
}

.a4-box-text h1 {
    color: #222;
    font-size: 24px;
}

.a4-box-text p {
    color: #888;
    font-size: 17px;
    font-weight: 300;
    line-height: 1.6;
    letter-spacing: -0.01em;
    margin-top: 12px;
}


/*==================================================*/
@media (max-width: 1250px) {
    .a4-left h1 {
        font-size: 45px;
    }

    .a4-left p {
        font-size: 16px;
    }
    
    .a4-box-wrapper {
        width: 500px;
    }

    .a4-vertical {
        left: -50px;
    }

    .a4-box-num {
        left: -67px;
        width: 35px;
        height: 35px;
        font-size: 14px;
    }

    .a4-box-text h1 {
        font-size: 20px;
    }

    .a4-box-text p {
        font-size: 16px;
        margin-top: 10px;
    }
}


@media (max-width: 950px) {
    .a4-wrapper {
        flex-direction: column;
        gap: 5rem;
    }

    .a4-left {
        position: unset;
    }

    .a4-left p {
        width: 450px;
        color: #666;
        margin-top: 1.5rem;
    }

    .a4-left p br {
        display: none;
    }

    .a4-left a {
        font-size: 15px;
        margin-top: 2rem;
    }

    .a4-box-wrapper {
        width: 100%;
        padding-left: 100px;
    }

    .a4-vertical {
        left: 40px;
    }

    .a4-box-num {
        left: -77px;
    }
}


@media (max-width: 550px) {
    .a4-wrapper {
        gap: 3rem;
    }

    .a4-left h1 {
        font-size: 32px;
    }
    
    .a4-left p {
        width: 100%;
        font-size: 15px;
        margin-top: 1.2rem;
    }

    .a4-left a {
        margin-top: 1.5rem;
    }

    .a4-box-wrapper {
        padding-left: 40px;
        gap: 3rem;
    }

    .a4-vertical {
        left: 10px;
    }

    .a4-box-num {
        top: 10px;
        left: -43px;
        width: 25px;
        height: 25px;
        font-size: 11px;
    }

    @keyframes pulseAnim {
        0% {
            box-shadow: 0 0 0 0 rgba(15, 155, 231, 50%);
        }

        70% {
            box-shadow: 0 0 0 8px rgb(151 213 229 / 0%);
        }

        100% {
            box-shadow: 0 0 0 0 rgb(151 213 229 / 0%);
        }
    }


    .a4-box-text {
        padding-top: 10px;
    }

    .a4-box-text h1 {
        font-size: 17px;
    }

    .a4-box-text p {
        font-size: 13px;
        margin-top: 5px;
    }
}


@media (max-width: 450px) {
    .article4 {
        padding-top: 80px;
    }
}