* {
    padding: 0;
    margin: 0;
    font-family: sans-serif;
    text-decoration: none;
}

body {
    background-color: whitesmoke;
    height: 2000px;
}

/* HEADER */

header {
    position: relative;
    width: auto;
    height: 100px;
    background-color: cadetblue;
    display: flex;
    flex-direction: row;
    justify-content: space-around;
    list-style: none;
}

    /* HEADER. logo */

.main_logo {
    position: absolute;
    border-top: 4px solid white;
    border-bottom: 4px solid white;
    left: 130px;
    top: 20px;
    color: white;
    font-family: sans-serif; 
    font-size: larger;
    font-weight: 500;
    text-align: center;
    border-radius: 4px;
    padding-bottom: 5px;
    transition: .3s;
}

.main_logo:hover {
    transform: scale(1.1);
}

.main_logo p {
    background-color: white;
    color: cadetblue;
    padding: -1px;
}

.main_logo a {
    text-decoration: none;
    color: white;
}

    /* HEADER. menu*/

header ul {
    display: flex;
    flex-direction: row;
    gap: 50px;
    align-items: center;
}

header li {
    list-style: none;
}

.menu li {
    position: relative;
    color: white;
    text-align: center;
    list-style: none;
}

.menu a {
    transition: all .5s;
    color: gray;
    font-weight: 600;
    display: block;
    padding-top: 10px;
    padding-bottom: 10px;
}

.menu a:hover {
    background-color: cadetblue;
    transition: .5s;
    color: aqua;
}

.menu ol {
    position: absolute;
    display: none;
    border-radius: 7px;
    margin-top: -3px;
    margin-left: -25px;
}

.menu li:hover ol {
    display: block;
    width: 200px;
    background-color: aquamarine;
    box-shadow: 1px 2px 2px 1px gray;
}

/* MAIN */

main {
    display: flex;
    flex-direction: row;
}

.main_txt {
    width: 700px;
    margin: 0 auto;
    margin-top: 100px;
    display: flex;
    flex-direction: column;
    gap: 70px;
}

/* flexbox */

.flexbox {
    display: flex;
    flex-direction: column;
    gap: 20px;
    text-align: justify;
}

.flexbox img {
    width: 500px;
    padding-top: 20px;
}

.flexbox ol {
    padding-left: 20px;
}

.flexbox ul {
    display: flex;
    flex-direction: column;
    gap: 30px;
    padding-left: 20px;
}

/* css_grid */

.css_grid {
    display: flex;
    flex-direction: column;
    gap: 20px;
    text-align: justify;
}

.css_grid ol {
    padding-left: 20px;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.css_grid ul {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-top: 10px;
    padding-left: 20px;
}

/* functions */

.functions {
    display: flex;
    flex-direction: column;
    gap: 20px;
    text-align: justify;
}

.functions ol {
    padding-left: 20px;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.functions ul {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-top: 10px;
    padding-left: 20px;
}

/* units */

.units {
    display: flex;
    flex-direction: column;
    gap: 20px;
    text-align: justify;
}

.units ol {
    padding-left: 20px;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.units ul {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-top: 10px;
    padding-left: 20px;
}

/* type_element */

.selectors {
    display: flex;
    flex-direction: column;
    gap: 20px;
    text-align: justify;
}

.selectors ol {
    padding-left: 20px;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.selectors ul {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-top: 10px;
    padding-left: 20px;
}

/* css_elements */

.css_elements h3 {
    margin-top: 30px;
    margin-bottom: 10px;
}

/* CSS LIST */

.css_list_box {
    display: flex;
    justify-content: flex-end;
    margin-top: 50px;
}

.css_list {
    position: absolute;
    position: fixed;
    float: left;
    display: flex;
    flex-direction: column;
    width: 200px;
    height: 500px;
    overflow-y: scroll;
    text-align: center;
    right: 100px;
}

.css_list a {
    color: cadetblue;
    display: block;
    font-weight: bold;
    height: 40px;
    padding-top: 5px;
    padding-bottom: 5px;
}

.css_list a:hover {
    background-color: aqua;
    color: grey;
}

/* grid_manual */

.grid_manual p {
    margin-top: 20px;
    margin-bottom: 20px;
}

/* adapt_design */

.adapt_design {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.adapt_design ul {
    padding-left: 30px;
    padding-top: 20px;
    padding-bottom: 20px;
}

.adapt_design li {
    padding-top: 10px;
    padding-bottom: 10px;
}

.adapt_design img {
    width: 700px;
}

/* bootstrap */

.bootstrap {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

/* psevdo_elements */

.psevdo_elements {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

/* animations */

.animations {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.animations ol, ul {
    display: flex;
    flex-direction: column;
    gap: 25px;
    margin-top: 10px;
    padding-left: 30px;
}

/* peremennie */

.peremennie {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.peremennie ol, ul {
    margin-top: 10px;
    padding-left: 30px;
}

/* mackets */

.mackets {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

/* ssilki */

.ssilki {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.ssilki ul, ol {
    padding-left: 25px;
}

/* FOOTER */

footer {
    background-color: cadetblue;
    height: 300px;
    margin-top: 100px;
}

footer ol {
    list-style: none;
    display: flex;
    flex-direction: row;
    justify-content: space-around;
    padding-top: 15px;
}

footer ul {
    display: flex;
    flex-direction: column;
    gap: 10px;
    list-style: none;
}

footer a {
    color: white;
    font-weight: 600;
}

footer a:hover {
    color: aqua;
}