:root {
    /* Material Design Dark Theme Palette */
    --primary-color: rgb(51, 153, 255);
    --primary-variant-color: #3700b3;
    --background-color: #121212;
    --surface-color: #1e1e1e;
    --text-color: rgba(255, 255, 255, 0.87);
    --subtle-text-color: rgba(255, 255, 255, 0.6);
}

body {
    font-family: 'Roboto', -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

main {
    flex-grow: 1;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* Header (App Bar) */
.top-nav {
    background-color: var(--surface-color);
    padding: 1rem 0;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
    z-index: 10;
}

.top-nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 2rem;
}

.logo {
    font-size: 1.5rem; /* Adjusted size for Material spec */
    font-weight: 500;
    color: var(--text-color);
    text-decoration: none;
}

.top-nav nav ul {
    margin: 0;
    padding: 0;
    list-style: none;
    display: flex;
    gap: 1.5rem;
}

.top-nav nav a {
    color: var(--subtle-text-color);
    text-decoration: none;
    font-size: 0.875rem; /* 14px */
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.089em;
    transition: color 0.3s ease;
}

.top-nav nav a:hover {
    color: var(--primary-color);
}

.auth-buttons {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.login-button, .register-button {
    text-decoration: none;
    font-weight: 500;
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.089em;
    border-radius: 4px;
    padding: 0.5rem 1rem;
    transition: background-color 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
    border: 1px solid transparent; /* For layout consistency */
    display: inline-block;
}

/* Text button style */
.login-button {
    color: var(--primary-color);
}

.login-button:hover {
    background-color: rgba(51, 153, 255, 0.1); /* primary color with low alpha */
}

/* Contained button style */
.register-button {
    color: var(--background-color);
    background-color: var(--primary-color);
    box-shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.24);
}

.register-button:hover {
    background-color: rgba(51, 153, 255, 0.75); /* Lighter shade */
    box-shadow: 0 3px 6px rgba(0,0,0,0.16), 0 3px 6px rgba(0,0,0,0.23);
}

/* Hero Section */
.hero {
    position: relative;
    text-align: center;
    padding: 6rem 1.5rem;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
}

#bg-video {
    position: absolute;
    top: 50%;
    left: 50%;
    min-width: 100%;
    min-height: 100%;
    width: auto;
    height: auto;
    z-index: 1;
    transform: translateX(-50%) translateY(-50%);
    background-size: cover;
    transition: 1s opacity;
    opacity: 0.25; /* Added to make text more readable */
}

.hero-content {
    position: relative;
    z-index: 2;
}

.hero h1 {
    font-size: 3.75rem; /* 60px */
    font-weight: 400;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.25rem; /* 20px */
    max-width: 600px;
    margin: 0 auto 2rem auto;
    color: var(--subtle-text-color);
    /* text-transform: uppercase; */
    letter-spacing: 0.089em;
    background-color: rgba(51, 153, 255, 0.15); /* --primary-color with 50% alpha */
    border: none;
    border-radius: 4px;
    text-decoration: none;
}

/* CTA Button (Raised Button) */
.cta-button {
    display: inline-block;
    padding: 0.75rem 2rem;
    font-size: 0.9rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.089em;
    color: var(--background-color);
    background-color: rgba(51, 153, 255, 0.75); /* --primary-color with 50% alpha */
    border: none;
    border-radius: 4px;
    text-decoration: none;
    transition: box-shadow 0.28s cubic-bezier(0.4, 0, 0.2, 1), background-color 0.2s;
    box-shadow: 0 3px 1px -2px rgba(0,0,0,.2),0 2px 2px 0 rgba(0,0,0,.14),0 1px 5px 0 rgba(0,0,0,.12);
}

.cta-button:hover {
    box-shadow: 0 2px 4px -1px rgba(0,0,0,.2),0 4px 5px 0 rgba(0,0,0,.14),0 1px 10px 0 rgba(0,0,0,.12);
    background-color: rgba(51, 153, 255, 1); /* Lighter shade on hover with increased opacity */
}

/* Footer */
footer {
    background-color: var(--surface-color);
    text-align: center;
    padding: 2rem 0;
    font-size: 0.875rem;
    color: var(--subtle-text-color);
}

/* --- Content Sections --- */

.content-section {
    padding: 4rem 0;
    text-align: center;
}

.content-section h2 {
    font-size: 2.5rem;
    font-weight: 400;
    margin-bottom: 3rem;
}

.alt-bg {
    background-color: var(--surface-color);
}


/* Features Section */
.features-container {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.features-row {
    display: flex;
    justify-content: center;
    gap: 2rem;
    flex-wrap: wrap;
}

.feature-card {
    background-color: var(--surface-color);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    display: flex;
    flex-direction: column;
    align-items: center;
    flex: 1 1 300px; /* Allow cards to grow and shrink */
    max-width: 350px; /* But not get too wide */
}

.feature-icon {
    display: none;
    width: 48px;
    height: 48px;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.3);
}

.feature-card h3 {
    font-size: 1.25rem;
    font-weight: 500;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

/* About Section */
.mission-text {
    max-width: 800px;
    margin: 0 auto;
    font-size: 1.1rem;
    line-height: 1.7;
    color: var(--subtle-text-color);
}

/* Contact Section */
.contact-form {
    max-width: 700px;
    margin: 2rem auto 0 auto;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    text-align: left;
}

.form-group {
    display: flex;
    gap: 1.5rem;
}

.form-group input {
    flex: 1;
}

.contact-form input,
.contact-form textarea {
    width: 100%;
    padding: 1rem;
    background-color: var(--surface-color);
    border: 1px solid rgba(255, 255, 255, 0.12);
    border-radius: 4px;
    color: var(--text-color);
    font-size: 1rem;
    font-family: inherit;
    box-sizing: border-box; /* Important for padding */
}

.contact-form input:focus,
.contact-form textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.contact-form ::placeholder {
    color: var(--subtle-text-color);
    opacity: 0.7;
}

.submit-button {
    align-self: flex-end;
    padding: 0.75rem 2rem;
    font-size: 0.9rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.089em;
    color: var(--background-color);
    background-color: var(--primary-color);
    border: none;
    border-radius: 4px;
    text-decoration: none;
    transition: box-shadow 0.28s cubic-bezier(0.4, 0, 0.2, 1), background-color 0.2s;
    box-shadow: 0 3px 1px -2px rgba(0,0,0,.2),0 2px 2px 0 rgba(0,0,0,.14),0 1px 5px 0 rgba(0,0,0,.12);
    cursor: pointer;
}

.submit-button:hover {
    box-shadow: 0 2px 4px -1px rgba(0,0,0,.2),0 4px 5px 0 rgba(0,0,0,.14),0 1px 10px 0 rgba(0,0,0,.12);
    background-color: rgba(51, 153, 255, 0.75);
}