:root {
    --font-family: 'Montserrat', sans-serif;
    --font-size: 18px;
    --font-weight: 400;
    --font-semi-bold: 500;
    --font-bold: 600;
    --font-color: #000000;
    --font-secondary-color: #4d4c52;
    --border: #0000001a;
    --foreground: #1a1919;
    --background: #ffffff;
    --secondary-background: #f9f9fa;
    --header-padding: 15px 15%;
    --header-content-width: 25%;
    --nav-display: flex;
    --svg-filter: none;
    --badge-background: #f0f0f0;
    --navbar-justify: space-between;
}

.dark-mode {
    --font-color: #dbdbdb;
    --font-secondary-color: #b0b0b0;
    --border: #262626;
    --foreground: #e0e0e0;
    --background: #0a0a0a;
    --secondary-background: #111111;

    --svg-filter: invert(100%) sepia(100%) saturate(2%) hue-rotate(20deg) brightness(102%) contrast(101%);
    --badge-background: #262626;
}

/* when screen width is less than 768px */
@media (max-width: 767px) {
    :root {
        --font-size: calc(8px + 1.5vw);
        --header-padding: 10px 5%;
        --header-content-width: 200%;
        --nav-display: none;
        --navbar-justify: center;
    }
}

input,
textarea,
button,
select,
a {
    -webkit-tap-highlight-color: transparent;
}

html {
    font-size: var(--font-size);
}

h1,
h2,
h3,
h4,
h5,
h6 {
    color: var(--font-color);
}

img {
    filter: var(--svg-filter);
}

* {
    box-sizing: border-box;
    font-family: var(--font-family);
    font-size: var(--font-size);
    font-weight: var(--font-weight);
}

body {
    margin: 0;
    padding: 0;
    background-color: var(--background);
}

p {
    line-height: 1.75;
}

header {
    border-bottom: 1px solid var(--border);
    border-top: 1px solid var(--border);
    display: flex;
    justify-content: var(--navbar-justify);
    align-items: center;
    padding: var(--header-padding);
    position: sticky;
    top: 0px;
    z-index: 1000;
    background-color: var(--background);
    opacity: 1;
    backdrop-filter: blur(10px);
}

.header-content {
    color: var(--foreground);
    width: var(--header-content-width);
    display: var(--nav-display);
}

.header-button {
    padding: 0px 12px;
    border: none;
    background: none;
    cursor: pointer;
}

.nav-content {
    text-align: center;
    display: flex;
    flex-direction: row;
    align-items: center;
    gap: 0.5em;
}

.nav-button img {
    height: 1em;
    width: 1em;
    margin: 0;
    padding: 0;
    display: inline-block;
    vertical-align: middle;
}

.nav-button {
    background: none;
    border: none;
    color: var(--font-color);
    font-size: 80%;
    font-weight: var(--font-bold);
    cursor: pointer;
    padding: 8px 12px;
    border-radius: 10px;
    transition: background 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
    /* float: right; */
}

.nav-button:hover {
    background: var(--secondary-background);
}

section {
    scroll-margin-top: 50px;
}

.hero {
    text-align: center;
    padding: 50px 0;
    position: relative;
    height: calc(100vh - 90px);
    scroll-margin-top: 80px;
}

.hero-content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, calc(-50%));
    width: 100%;
    padding: 0px 5%;
}

.hero h1 {
    font-size: 3rem;
    font-weight: var(--font-semi-bold);
    margin-bottom: 20px;
}

.hero p {
    font-size: 1.25rem;
    color: var(--font-secondary-color);
    margin: 0;
}

.hero-content div {
    margin-top: 30px;
    margin-bottom: 50px;
}

li::marker {
    color: var(--font-secondary-color);
}

ul {
    margin: 14px 0;
}

li p {
    margin: 0;
}

button {
    background: none;
    border: 1px solid var(--border);
    font-size: 80%;
    font-weight: var(--font-semi-bold);
    cursor: pointer;
    padding: 8px 24px;
    border-radius: 10px;
    transition: background 0.3s;
}

a {
    background: none;
    border: 1px solid var(--border);
    font-size: 80%;
    font-weight: var(--font-semi-bold);
    cursor: pointer;
    padding: 2px;
    border-radius: 10px;
    transition: background 0.3s;
    text-decoration: none;
    text-align: center;
}

a > img {
    width: 75%;
    margin-top: 15%;
}

.button-black {
    background: var(--font-color);
    color: var(--background);
    transition: background 0.3s;
    padding: 15px 24px;
}

.button-black:hover {
    background: var(--foreground);
}

button:hover {
    background: var(--secondary-background);
}

a:hover {
    background: var(--secondary-background);
}

.skills {
    color: var(--font-secondary-color)
}

.content-section {
    position: relative;
    width: 100%;
    padding: 50px 0;
}

.content-section > div > h1 {
    text-align: center;
    font-size: 2rem;
    font-weight: var(--font-weight);
    margin-bottom: 5px;
}

.content-section > div > p {
    text-align: center;
    color: var(--font-secondary-color);
    margin: 0 5%;
}

.content-section h2 {
    margin-top: 0;
}

.research {
    background: var(--secondary-background);
}

.row {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    padding: 0 5%;
}

.row-1 {
    margin-top: 30px;
}

.card {
    background: var(--background);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 20px 16px;
    margin: 10px 12px;
    width: 475px;
    transition: transform 0.3s;
}

.card h2 {
    font-size: 0.875rem;
    margin: 0;
    font-weight: var(--font-semi-bold);
    width: 85%;
    line-height: 1.5;
}

.card p {
    font-size: 0.875rem;
    color: var(--font-secondary-color);
}

.card:hover {
    transform: translateY(-2px);
}

.project-title {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

.badge {
    background: var(--badge-background);
    border-radius: 10px;
    color: var(--font-color);
    display: inline-block;
    font-size: 70%;
    font-weight: var(--font-bold);
    margin: 4px 2px;
    padding: 4px 8px;
    transition: background 0.3s;
}

footer {
    text-align: center;
    padding: 20px;
    /* border-top: 1px solid var(--border); */
    color: var(--font-secondary-color);
}

footer p {
    margin: 0;
    font-size: 0.75rem;
}