:root {
    --navy: #101e32;
    --blue: #1668bd;
    --blue-hover: #0f559d;
    --ink: #172338;
    --muted: #526174;
    --background: #f5f7fa;
    --white: #ffffff;
    --border: #e3e8ef;
}

/* Global Reset */
* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    padding: 0;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 16px;
    line-height: 1.75;
    color: var(--ink);
    background: var(--background);
}

/* Header */
header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    padding: 20px 40px;

        color: var(--white);
}

header strong {
    font-size: 22px;
    font-weight: 700;
    line-height: 1.4;
}

header a {
    color: var(--white);
    text-decoration: none;
    transition: color 0.3s ease;
}

header a:hover {
    color: #a9d3ff;
}

/* Main Container */
main {
    width: 100%;
    max-width: 1050px;
    margin: 44px auto;
    padding: 0 22px;
}

/* Article */
article {
    background: var(--white);
    border-radius: 12px;
    padding: 36px 42px;
    box-shadow: 0 5px 25px rgba(16, 30, 50, 0.06);
}

/* Headings */
h1 {
    margin: 0 0 24px;
    font-size: 36px;
    font-weight: 700;
    line-height: 1.25;
    color: var(--navy);
}

h2 {
    margin: 34px 0 16px;
    font-size: 23px;
    font-weight: 700;
    line-height: 1.4;
    color: var(--navy);
}

h3 {
    margin: 24px 0 12px;
    font-size: 19px;
    font-weight: 600;
    color: var(--navy);
}

/* Paragraphs */
p {
    margin: 0 0 18px;
    font-size: 16px;
    line-height: 1.8;
}

/* Lists */
ul,
ol {
    margin: 0 0 20px;
    padding-left: 25px;
}

li {
    margin-bottom: 10px;
    font-size: 16px;
    line-height: 1.8;
}

/* Links */
a {
    color: var(--blue);
    text-decoration: none;
    transition: color 0.3s ease;
}

a:hover {
    color: var(--blue-hover);
    text-decoration: underline;
}

/* Note Box */
.note {
    margin: 20px 0;
    padding: 15px 18px;
    background: #fff4d8;
    border-left: 4px solid #c47c00;
    border-radius: 4px;
    color: var(--ink);
}

/* Small Text */
.small {
    font-size: 14px;
    line-height: 1.6;
    color: var(--muted);
}

/* Buttons */
button,
.btn {
    display: inline-block;
    padding: 10px 18px;
    background: var(--blue);
    color: var(--white);
    border: none;
    border-radius: 6px;
    font-family: inherit;
    font-size: 15px;
    font-weight: 600;
    line-height: 1.5;
    text-decoration: none;
    cursor: pointer;
    transition: background 0.3s ease;
}

button:hover,
.btn:hover {
    background: var(--blue-hover);
    color: var(--white);
    text-decoration: none;
}

button:focus-visible,
a:focus-visible {
    outline: 3px solid #78b9ff;
    outline-offset: 3px;
}

/* Footer */
footer {
    margin-top: 55px;


    color: var(--white);
    text-align: center;
}

footer p {
    margin-bottom: 10px;
}

footer a {
    display: inline-block;
    margin: 0 8px;
    color: var(--white);
    font-size: 14px;
}

footer a:hover {
    color: #a9d3ff;
}

/* Tablet */
@media (max-width: 768px) {
    header {
        padding: 18px 24px;
    }

    main {
        margin: 30px auto;
        padding: 0 18px;
    }

    article {
        padding: 28px;
    }

    h1 {
        font-size: 32px;
    }

    h2 {
        font-size: 22px;
    }
}

/* Mobile */
@media (max-width: 650px) {
    header {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
        padding: 16px 20px;
    }

    header strong {
        font-size: 17px;
    }

    main {
        margin: 20px auto;
        padding: 0 12px;
    }

    article {
        padding: 22px 18px;
        border-radius: 8px;
    }

    h1 {
        font-size: 29px;
        line-height: 1.3;
    }

    h2 {
        margin-top: 28px;
        font-size: 21px;
    }

    h3 {
        font-size: 18px;
    }

    p,
    li {
        font-size: 15px;
        line-height: 1.75;
    }

    footer {
        margin-top: 35px;
        padding: 22px 15px;
    }

    footer a {
        margin: 5px 8px;
    }

    button,
    .btn {
        padding: 10px 15px;
    }
}