:root {
    /* Core Variables */
    --spacing-unit: 1rem;
    --container-width: 1000px;
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --transition-speed: 0.2s;

    /* Default Theme (Dark) */
    --bg-color: #111111;
    --bg-card: #1a1a1a;
    --text-main: #ffffff;
    --text-secondary: #a1a1a1;
    --border-color: #333333;
    --accent-color: #ffffff; /* Using white as accent for dark mode */
    --brand-accent: #3b82f6; /* Subtle Blue link color */

    /* Strict Rule: Brand Title Always White */
    --brand-title-color: #ffffff;
}

[data-theme="light"] {
    --bg-color: #ffffff;
    --bg-card: #f9f9f9; /* Subtle difference for cards */
    --text-main: #111111;
    --text-secondary: #666666;
    --border-color: #eaeaea;
    --accent-color: #111111;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    transition: background-color 0.3s ease, color 0.3s ease;
}

a {
    text-decoration: none;
    color: inherit;
    transition: opacity var(--transition-speed) ease;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
}

/* Header */
.header {
    padding: 2rem 0;
    position: relative;
    z-index: 10;
}

.header-content {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.header-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.header-divider {
    border: 0;
    height: 1px;
    background-color: var(--border-color);
    width: 100%;
    margin: 0;
}

.header-nav {
    display: flex;
    justify-content: center;
    gap: 3.5rem;
    width: 100%;
}

.brand-logo {
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    color: var(--text-main); /* Adaptive */
}

/* Theme Toggle */
.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-main);
    padding: 0.5rem;
    border-radius: 50%;
    transition: background-color 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background-color: rgba(128, 128, 128, 0.1);
}

.icon-sun {
    display: none;
}
.icon-moon {
    display: block;
}

[data-theme="light"] .icon-sun {
    display: block;
}
[data-theme="light"] .icon-moon {
    display: none;
}

/* Main */
main {
    display: flex;
    flex-direction: column;
    gap: 6rem;
    margin-bottom: 6rem;
}

/* Footer */
.footer {
    padding: 3rem 0;
    text-align: center;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-top: auto;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}