:root {
    /** ============ CSS-змінні ============ */
    --color-font-body: #220c0c;
    --color-background-body: #e1ffde;
    --color-title-lesson: #4b4200;
    --color-title-section: red;
    --color-title-subsection: blue;
}

body {
    font-family: 'Montserrat', serif;
    font-size: 1.5rem;
    padding: 20px 20px 150px;
    /* min-height: 100vh; */
    display: flex;
    flex-direction: column;
    gap: 20px;
    /* flex-wrap: wrap; */
    /* justify-content: center; */
    /* text-align: center; */
    align-items: center;
    color: var(--color-font-body);
    background-color: var(--color-background-body);
}

.title-lesson {
    text-align: center;
    color: var(--color-title-lesson);
    text-shadow: 4px 2px 6px #43300088;
    /* ! for position: fixed */
    /* margin-bottom: 350px; */
}

.title-section {
    margin-top: 20px;
    margin-bottom: 10px;
    text-align: center;
    color: var(--color-title-section);
    text-shadow: 4px 2px 6px #a17301bd;
}

.title-subsection {
    margin-top: 10px;
    margin-bottom: 15px;
    font-style: italic;
    color: var(--color-title-subsection);
    text-shadow: 4px 2px 6px #0114a1bd;
}

.part {
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    /* outline: 1px solid red; */
}

/* *======================================= */
/* ! */
/* .part_1 {
    display: none;
} */
/*! 1.position: static */
.part_1 .father {
    width: 500px;
    height: 200px;
    margin-bottom: 20px;
    color: red;
    background: #fffdd6;
    outline: 4px double rgb(61, 56, 0);
}

.part_1 .title {
    position: static; /* ! */
    left: 10%;
    top: 10%;
    font-size: 1.5rem;
    color: var(--color-font-body);
    background: #b8f1ff;
    outline: 1px dashed green;
}

.part_1 .title::after {
    content: '(::after - без позиціонування)';
    margin-left: 5px;
    font-size: initial;
    font-style: italic;
    color: initial;
    outline: 1px dashed #ff6d6d;
}

.part_1 .child {
    width: 70%;
    height: 6rem;
    color: initial;
    background: #fffaa5;
    outline: 1px dotted blue;
}


/* ! */
/* .part_2 {
    display: none;
} */
/*! 2.position: relative */
.part_2 .father {
    width: 500px;
    height: 200px;
    margin-bottom: 20px;
    color: red;
    background: #fffdd6;
    outline: 4px double rgb(61, 56, 0);
}

.part_2 .title {
    /* position: static; */
    position: relative; /* ! */
    /* todo var.1 */
    left: 10%;
    top: 10%;
    /* todo var.2 */
    left: 50px;
    top: 20px;
    font-size: 1.5rem;
    color: var(--color-font-body);
    background: #b8f1ff;
    outline: 1px dashed green;
}

.part_2 .title::after {
    content: '(::after - left: 10%; top: 10%;)';
    margin-left: 5px;
    font-size: initial;
    font-style: italic;
    color: initial;
    outline: 1px dashed #ff6d6d;
}

.part_2 .child {
    width: 70%;
    height: 6rem;
    color: initial;
    background: #fffaa5;
    outline: 1px dotted blue;
}


/* ! */
.part_31 {
    display: none;
}
/*! 3-1.position: absolute від <body> */
.part_31 .father {
    width: 500px;
    height: 200px;
    margin-bottom: 20px;
    color: red;
    background: #fffdd6;
    outline: 4px double rgb(61, 56, 0);
}

.part_31 .title {
    /* position: static; */
    /* position: relative; */
    position: absolute; /* ! */
    left: 10%;
    top: 10%;
    font-size: 1.5rem;
    color: var(--color-font-body);
    background: #b8f1ff;
    outline: 1px dashed green;
}

.part_31 .title::after {
    content: '(::after - left: 10%; top: 10%; від <body>)';
    margin-left: 5px;
    font-size: initial;
    font-style: italic;
    color: initial;
    outline: 1px dashed #ff6d6d;
}

.part_31 .child {
    width: 70%;
    height: 6rem;
    color: initial;
    background: #fffaa5;
    outline: 1px dotted blue;
}


/* ! */
/* .part_32 {
    display: none;
} */
/*! 3-2.position: absolute від <father> */
.part_32 .main-father {
    width: 500px;
    height: 200px;
    outline: 4px double rgb(4, 0, 61);
}

.part_32 .father {
    position: relative; /* ! */
    /* left: 10%; */
    /* top: 10%; */
    width: 500px;
    height: 200px;
    margin-bottom: 20px;
    color: red;
    background: #fffdd6;
    outline: 4px double rgb(61, 56, 0);
}

.part_32 .title {
    /* position: static; */
    /* position: relative; */
    position: absolute; /* ! */
    left: 10%;
    top: 10%;
    width: 516px;
    font-size: 1.5rem;
    color: var(--color-font-body);
    background: #b8f1ff;
    outline: 1px dashed green;
}

.part_32 .title::after {
    content: '(::after - left: 10%; top: 10%; від <father>)';
    margin-left: 5px;
    font-size: 13px;
    font-style: italic;
    color: initial;
    outline: 1px dashed #ff6d6d;
}

.part_32 .child {
    width: 70%;
    height: 6rem;
    color: initial;
    background: #fffaa5;
    outline: 1px dotted blue;
}


/* ! */
.part_4 {
    /* display: none; */
    height: auto;
}
/*! 4.position: fixed */
.part_4 .father {
    width: 500px;
    /* height: 100px; */
    margin-bottom: 20px;
    color: red;
    background: #fffdd6;
    outline: 4px double rgb(61, 56, 0);
}

.part_4 .title {
    position: static;
    font-size: 1.5rem;
    color: var(--color-font-body);
    background: #b8f1ff;
    outline: 1px dashed green;
}

.part_4 .title::after {
    content: '(::after - без позиціонування)';
    margin-left: 5px;
    font-size: initial;
    font-style: italic;
    color: initial;
    outline: 1px dashed #ff6d6d;
}

.part_4 .child {
    width: 70%;
    /* height: 3rem; */
    color: initial;
    background: #fffaa5;
    outline: 1px dotted blue;
}

/*? КНОПКИ */
/*? Кнопка-догори (загальні стили) */
.part_4 .arrow-button {
    /* ! */
    /* position: fixed; */
    /* ? */
    /* top: 30px; */
    right: 30px;
    align-self: flex-start;
    display: inline-block;
    margin: 0;
    padding: 10px;
    font-family: monospace;
    font-size: 20px;
    font-weight: 700;
    color: red;
    border: 2px solid red;
    border-radius: 8px;
    background-color: #a2cfff;
    cursor: pointer;
}
/* ? Кнопка-догори */
.part_4 .up-button {
    top: 30px;
}
/* ? Кнопка-донизу */
.part_4 .down-button {
    align-self: flex-end;
    bottom: 30px;
}


/* ! */
.part_5 {
    /* display: none; */
    height: auto;
}
/*! 5.position:sticky */
.part_5 .father {
    width: 500px;
    /* height: 100px; */
    margin-bottom: 20px;
    color: red;
    background: #d6ffe7;
    outline: 4px double rgb(61, 56, 0);
}

.part_5 .child {
    width: 70%;
    margin: 0 auto;
    /* height: 3rem; */
    color: initial;
    background: #9cfec5;
    outline: 1px dotted blue;
}

.part_5 .child img{
    margin: 10px auto;
    background: #fef39c;
}
.part_5 .child img:first-child{
    background: #edc2fd;
}

.part_5 .title {
    width: 100%;
    position: sticky;
    top: 0;
    /* left: 10px; */
    font-size: 1.5rem;
    text-align: center;
    color: var(--color-font-body);
    background: #ffb8f2;
    /* outline: 1px dashed green; */
}

.part_5 p + img + .title {
    background: #fffb80;
}



/* ! */
/* .part_6 {
    display: none;
} */
/*! 6.Властивість z-index */
.part_6 .container {
    width: 500px;
    height: 400px;
    position: relative;
    outline: 4px double rgb(61, 56, 0);
}

.part_6 .box {
    position: absolute;
    height: 150px;
    width: 150px;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 4px;
    font-size: 64px;
    color: #fff;
    box-shadow: 0px 2px 1px -1px rgba(0, 0, 0, 0.2),
        0px 1px 1px 0px rgba(0, 0, 0, 0.14), 0px 1px 3px 0px rgba(0, 0, 0, 0.12);
}

.part_6 .box:nth-child(1) {
    top: 20px;
    left: 130px;
    background-color: #1789fc;
    z-index: 2;
}

.part_6 .box:nth-child(2) {
    top: 30px;
    left: 230px;
    background-color: #ef233c;
    z-index: 2;
}

.part_6 .box:nth-child(3) {
    top: 140px;
    left: 220px;
    background-color: #ffd07b;
    z-index: 1;
}

.part_6 .box:nth-child(4) {
    top: 120px;
    left: 120px;
    background-color: #4caf50;
}














/* ! */
.part_7 {
    display: none;
}
/*! 7.HW-25 */
.part_7 .container {
    width: 100px;
    height: 300px;
    outline: 1px solid red;
    /* todo var.2 */
    /* position: relative; */
}

.part_7 .box {
    width: 100px;
    height: 100px;
    display: flex;
    justify-content: flex-end;
}

.part_7 .box1 {
    background-color: lightcoral;
}

.part_7 .box2 {
    z-index: 1;
    /* todo var.1 */
    position: relative;
    left: 50px;
    top: -50px;
    background-color: cornflowerblue;
    /* todo var.2 */
    /* position: absolute;
    left: 50px;
    top: 50px; */
}

.part_7 .box3 {
    position: relative;
    left: 100px;
    top: -100px;
    background-color: lime;
    /* todo var.2 */
    /* position: absolute;
    left: 100px;
    top: 100px; */
}




/*? ______________________________________________________ */
/* ! */
.part_0 {
    display: none;
}
/*! 0.Заголовок */