:root {
    /* COLOR PALETTE */
    --light: #ffffff;
    --dark: #000000;
    --accent: #1600e0;
    --accent-soft: hsla(246, 100%, 44%, 0.1);
    --grey-light: #E5E5E5;
    --grey-medium: #8d8d8d;

    /* TYPOGRAPHY */
    --font-primary: "Sora", sans-serif;
    --font-secondary: "Source Code Pro", monospace;
    
    --fs-base: 1rem;       /* 16px */
    --fs-small: 0.625rem;  /* 10px - Footer */
    --fs-button: 1.25rem;  /* 20px - Buttons */
    --fs-sub: 2rem;        /* 32px - Sub Headings */
    --fs-heading: 2.5rem; /* 40px - Main Headings */
    
    --lh-base: 2;    
    --lh-tight: 1.2;

    --lsp: 1px;

    /* SPACING & SIZING */
    --space-xs: 0.5rem;
    --space-sm: 1rem;
    --space-md: 2rem;
    --space-lg: 4rem;

    /* UI ELEMENTS */
    --btn-radius: 15px;
    --radius: 30px;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
    
    --transition: 0.2s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: var(--font-primary);
}

header {
    padding: var(--space-lg);
    text-align: center;
    overflow-x: hidden;
}

section {
    padding: var(--space-lg);
    text-align: center;
    overflow: hidden;
}

h1, h2 {
    text-transform: capitalize;
    font-size: var(--fs-heading);
    font-weight: 600;
    line-height: var(--lh-tight);
}

p {
    line-height: var(--lh-base);
}

.flex-gap {
    display: flex;
    gap: var(--space-md);
}

.flex-center {
    display: flex;
    justify-content: center;
    align-items: center;
}

.flex-column {
    flex-direction: column;
}

.absolute-center {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.button {
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--btn-radius);
    text-transform: uppercase;
    font-family: var(--font-secondary);
    color: var(--light);
    background-color: var(--dark);
    text-decoration: none;
    letter-spacing: var(--lsp);
    z-index: 10;
    transition: var(--transition);
    border: 2px solid var(--dark);
}

#menu-list.is-active {
    display: flex;
    z-index: 200;
}

header nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

header #logo {
    display: block;
    line-height: 0;
}

header #logo img {
    width: 50px;
    height: auto;
}

header #menu-toggle {
    background: transparent;
    border: none;
    cursor: pointer;
}

header #menu-list {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);

    background-color: var(--light);

    text-align: center;
    list-style-type: none;

    border-radius: var(--radius);
    box-shadow: var(--shadow);

    width: 80%;
    height: 70%;

    flex-direction: column;
    align-items: center;
    justify-content: center;

    gap: var(--space-lg);

    display: none;
}

header #menu-list li a {
    font-family: var(--font-secondary);
    text-transform: uppercase;
    text-decoration: none;
    color: var(--dark);
    padding: var(--space-md);
    letter-spacing: var(--lsp);
}

header #menu-list li a:hover {
    font-weight: 700;
}

/* HERO */

#hero h1 {
    z-index: 10;
}

#hero p {
    line-height: var(--lh-base);
    z-index: 10;
}

.hero-text a {
    margin-top: var(--space-md);
}

.hero-text a:hover {
    background-color: var(--light);
    color: var(--dark);
}

.hero-visual-anchor {
    display: grid;
    place-items: center; 
    margin: var(--space-lg) auto;
    width: 100%;
    max-width: 500px;       
    position: relative;
    margin-top: -25%;
}

.hero-visual-anchor picture,
.circle {
    grid-area: 1 / 1; 
}

.hero-visual-anchor picture {
    z-index: 2;
}

.hero-img {
    display: block;
    width: 100%;
    height: auto;
}

.circle {
    z-index: 1;          
    border: 1px solid var(--grey-light);
    border-radius: 50%;
    aspect-ratio: 1 / 1;
}

.large  { width: 250%; }
.medium { width: 175%; }
.small  { width: 100%; }


/* HOW IT WORKS */

#how {
    position: relative;
    margin-top: -15rem;
    z-index: 20;
}

.how-visual {
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    width: 100%;
    padding-block: var(--space-lg);
}

.card-stack {
    display: flex;
    flex-direction: column; 
    align-items: center;  
    position: relative;
    z-index: 5;         
    padding-top: var(--space-lg);
}

.how-visual img {
    width: 300px;
    height: auto;
    position: relative;
}

.how-visual img:nth-of-type(1) {
    margin-left: -100px;  
}
.how-visual img:nth-of-type(2) {
    margin-top: -150px; 
    margin-left: 100px;  
}

.curves {
    width: 150vw; 
    max-width: none; 
    
    height: auto;
    z-index: -10;
    pointer-events: none; 
}

/* SYSTEMS */

#system {
    position: relative;
}

#system .curves {
    top: 80%;
}

.system-visual {
    width: 100%;
    padding-block: var(--space-lg);
}

.system-visual picture img {
    width: 500px;
    height: auto;
    object-fit: cover;
}

/* FOOTER */

footer {
    padding: 0 var(--space-md) var(--space-lg);
    font-size: var(--fs-small);
}

#footer-content {
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: var(--space-md);
}

#footer-content .important-info .logo {
    padding-block: var(--space-md);
}

#footer-content .important-info .logo img {
    width: 50px;
    height: auto;
}

#footer-content .important-info .logo strong {
    font-size: 2rem;
}

#footer-content .important-info p {
    text-align: center;
}

#socials {
    padding-block: var(--space-md);
}

#socials ul {
    list-style-type: none;
}

#links {
    padding-block: var(--space-sm);
}

#links ul {
    list-style-type: none;
    padding-block: var(--space-sm);
}

#links ul li {
    padding: .7rem 2rem;
}

#links ul li a:hover {
    font-weight: 600;
}

#links a {
    text-decoration: none;
    color: var(--dark);
}

#links {
    display: grid;
    grid-template-columns: 1fr 1fr;

    text-align: center;
}

hr {
    visibility: hidden;
}

.copyright-info {
    padding-block: var(--space-sm);
    gap: .5rem;
    flex-direction: column;
}

.copyright-info small {
    text-transform: uppercase;
    letter-spacing: .5px;
    color: var(--grey-medium);
    text-align: center;
    font-family: var(--font-secondary);
}



@media screen and (min-width: 700px) {
    :root {
        --fs-small: 0.875rem; 
        --fs-sub: 3rem;       
        --fs-heading: 4rem; 
        
    }
    
    h1, h2 {
        max-width: 20ch;
    }

    p {
        max-width: 60ch;
    }

    header {
        padding: var(--space-md) 15vw;

    }

    header nav {
        display: flex;
        align-items: center;
        justify-content: space-between;
    
        background: var(--light);
        padding: var(--space-md) var(--space-lg);
        border-radius: 50em;
        box-shadow: var(--shadow);
    }

    header #menu-toggle {
        display: none;
    }

    header #menu-list {
        transform: none;
        width: auto;
        height: auto;
        box-shadow: none;

        display: flex;
        flex-direction: row;

        gap: var(--space-sm);

        position: static;
    }

    header #menu-list li a {
        font-size: var(--fs-small);
    }

    #hero { 
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
    }

    .hero-visual-anchor {
        max-width: 700px;
        margin-top: -10%;
    }

    .large  { width: 150%; }
    .medium { width: 100%; }
    .small  { width: 50%; }

    /* HOW IT WORKS */

    .how-visual img {
        width: 700px;
    }

    .how-visual img:nth-of-type(2) {
        margin-top: -250px; 
    }

    .curves {
        top: 0;
    }

    /* SYSTEM */

    .system-visual {
        width: 100%;
        padding-block: var(--space-lg);
    }

    .system-visual picture img {
        width: auto;
        height: auto;
        object-fit: cover;
    }

    /* FOOTER */

    footer {
        padding: 0 var(--space-lg) var(--space-lg);
    }

    #footer-content {
        display: grid;
        grid-template-columns: 2fr 1fr 1fr;
        padding: var(--space-md) calc(var(--space-lg)*2);
        align-items: start;
    }
    
    #footer-content .important-info .logo {
        justify-content: start;
    }

    #footer-content .important-info p {
        text-align: left; 
        max-width: 35ch;  
    }

    #socials ul {
        justify-content: start;
    }

    #links {
        display: contents; 
    }

    #links .product, #links .references {
        margin-top: 80px;
        justify-self: end;
    }

    #links ul li {
        padding: 0.8rem 0; 
    }

    hr {
        visibility: visible;
        grid-column: 1 / -1; 
        border: 0;
        border-top: 1px solid var(--grey-light);
        margin-block: var(--space-md);
    }

    .copyright-info {
        grid-column: 1 / -1; 
        flex-direction: row; 
        justify-content: space-between; 
        align-items: center;
    }

    .copyright-info small {
        text-align: left;
    }
}