* {
    font-family: system-ui;
    font-weight: 400;
    font-size: 20px;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth; 
}

body {
    overflow-x: hidden;
}

.header {
    position: sticky;
    top: 0;
    z-index: 1000;
    height: 2.5rem;
    width: 100%;
}

.header__container_elements {
    display: flex;
    background: rgba(0, 0, 0, .85);
    backdrop-filter: saturate(180%) blur(20px);
    height: 100%;
    width: 100%;
    flex-flow: row nowrap;
    justify-content: space-between;
    padding: 0 9.5rem;
    align-items: center;
}

.symbol {
    font-size: 1.4rem;
}

.symbol:hover {
    filter:drop-shadow(0 0 .1111rem #fff);
}

.header a {
    color: rgb(142, 142, 142);
    font-size: 15px;
    transition: color .2s;
}

.header a:hover {
    color: #fff;
    text-decoration: none;
}

.main__big-title {
    background: rgb(248, 249, 250);
    height: 23.5rem;    
    margin: .7rem .7rem 0 ;
    position: relative;
    display: flex;
    justify-content: center;
    overflow: hidden;
}

.main__big_title_text {
    align-self: center;
    width:41.66666667%;
    text-align: center;
    padding: 2rem;
    position: relative;
}

.main__text_title {
    font-size: calc(1.175rem + 2.7vw);
    margin-bottom: .5rem;
}

.main__big_title_button {
    height: 1.8rem;
    width: 6rem;
    font-size: .8rem;
    margin-top: 1rem;
    border-radius: 5px;
    color: rgb(108, 117, 125);
    border: 1px solid rgb(108, 117, 125);
    background: #fff;
    transition: background .3s, color .6s;
}

.main__big_title_button:hover {
    background: rgb(108, 117, 125);
    color: rgb(248, 249, 250);
}

.main_big-title_cellphone {
    display: flex;
    width: 13rem;
    height: 24rem;
    background-color: #333;
    border-radius: 21px;
    transform: rotate(30deg);
    position: absolute;
    align-items: center;
}

.main__celphone_screen {
    width: 12rem;
    height: 20rem;
    background: rgba(72, 72, 72);
    border-radius: 5px;
    margin: auto;
    transition: box-shadow 1s, background .5s;
}

.position_cellphone {
    left: 70%;
    top: 25%;
}

.white_cellphone {
    background-color: rgb(232,232,232);
    bottom: 5rem;
    left: 3rem;
}

.white_cellphone .main__celphone_screen {
    background: rgb(232, 232, 232);
}

.main_big-title_cellphone:hover>.main__celphone_screen {
    box-shadow: 0 0 10px #fff;
    background: #fff;
}

.main__group_cards_headline {
    width: 100%;
    display: flex;
    flex-flow: row wrap;
    padding: 0.7rem 0 0 0.7rem;
    justify-content: space-between;
    align-content:stretch;
}

.main__card-container {
    display: flex;
    flex-direction: column;
    height: 25rem;
    flex: 35%;
    background: rgb(248, 249, 250);
    margin-right:0.7rem;
    padding: 3rem 3rem 0 3rem;
    text-align: center;
    justify-content: center;
    overflow: hidden;
}

.main_group-cards_text {
    margin: 1rem 0 ;
    color: rgba(33, 37, 41);
    max-width: 22rem;
    align-self: center;
}

.group_cards_title {
    font-size:calc(1rem + 2.1vw);
    font-weight: 300;
}

.main_group-cards_text p {
    font-weight: 100;
}

.main__group_cards-phone {
    height: 20rem;
    width: 20rem;
    min-width: 12rem;
    background-color:rgb(248, 249, 250);
    position: relative;
    top: 1rem;
    border-radius: 1rem;
    align-self: center;
    transition: box-shadow .3s;
}

.phone-hover:hover {
    box-shadow:0 0 15px #fff
}

.black-box {
    background: rgba(33, 37, 41);
}

.w-text {
    color: rgb(248, 249, 250);
}

.b-phone {
    background-color: rgba(33, 37, 41);
}

.bl-box {
    background-color: rgb(13,110,253);
}

.f-w-phone {
    background: rgba(255, 255, 255);
}


.footer__row {
    display: flex;
    flex-direction: row;
    justify-content: center;
}

.footer__block-list {
    margin: 2rem 3.5rem 2rem 0;
}

.footer__block-list i {
    display: block;
    font-size: 1.5rem;
}

.footer__ul {
    list-style: none;
}    


.footer__ul a{
    font-size: .8rem;
    color: #6c757d;
} 



@media only screen and (max-width: 870px) {
    .header__container_elements {
        display: flex;
        justify-content:center ;
    }

    .header__container_elements a{
        display: none;
    }

    .header__container_elements a:first-child {
        display: block;
    }

    .main__group_cards-phone {
        width: 15rem;
    }
}

@media only screen and (max-width: 706px) {
    .main__group_cards-phone {
        width: 12rem;
    }

    .footer__row {
        flex-wrap: wrap;
    }
}


@media only screen and (max-width: 540px) {
    .main__big-title {
        margin: 0;
    }

    .main__big_title_text {
        width:auto;
    }

    .main_big-title_cellphone {
        display: none;
    }

    .main__group_cards_headline {
        display: flex;
        flex-direction: column;
        width: 100%;
        padding: 0;
    }

    .main__group_cards-phone {
        width: 17.5rem;
    }

    .main__card-container {
        margin: 0;
        padding:0 .5rem;
    }

    .footer__row {
        justify-content: start;
    }

    .footer__block-list {
        margin: .5rem;
    }
}



@media only screen and (max-width: 390px) {
    .main__big-title {
        height: 16.5rem;
    }

    .main__big_title_text {
        padding: .3rem;
    }

    .header__container_elements {
        padding: 0%;
    }

    .main__group_cards-phone {
        width: 7rem;
    }

    .main__card-container {
        padding:0 .1rem;
    }

}