:root {
    --bg-dark: #1A1D20;
    --bg-card: #24282C;
    --accent-green: #007500;
    --accent-green-bright: #00B027;
    --text-main: #F4F6F8;
    --text-muted: #A0AAB2;
    --border-color: #33383F;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

body {
    background-color: var(--bg-dark);
    color: var(--text-main);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    -webkit-text-size-adjust: 100%;
}

header {
    background-color: rgba(26, 29, 32, 0.95);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(8px);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.brand-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 1.4rem;
    font-weight: 800;
    letter-spacing: 1px;
    cursor: pointer;
}

.brand-logo span.nis { color: var(--accent-green-bright); font-style: italic; }
.brand-logo span.topes { color: var(--text-main); font-style: italic; }

nav ul {
    display: flex;
    list-style: none;
    gap: 1.2rem;
    flex-wrap: wrap;
}

nav a {
    color: var(--text-muted);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.95rem;
    transition: color 0.2s;
    cursor: pointer;
    padding: 0.3rem 0;
}

nav a:hover, nav a.active {
    color: var(--accent-green-bright);
}

.page-view {
    display: none;
    max-width: 1200px;
    margin: 0 auto;
    padding: 2.5rem 1.5rem;
    flex: 1;
    width: 100%;
}

.page-view.active {
    display: block;
}

.hero {
    text-align: center;
    padding: 3rem 1rem;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1.2rem;
    line-height: 1.2;
}

.hero h1 span { color: var(--accent-green-bright); }

.hero p {
    font-size: 1.1rem;
    color: var(--text-muted);
    max-width: 800px;
    margin: 0 auto 2rem;
}

.btn {
    background-color: var(--accent-green);
    color: #fff;
    padding: 0.75rem 1.5rem;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 600;
    display: inline-block;
    border: none;
    cursor: pointer;
    transition: background 0.2s;
    font-size: 0.95rem;
    text-align: center;
}

.btn:hover { background-color: var(--accent-green-bright); }

.btn-secondary {
    background-color: transparent;
    border: 1px solid var(--accent-green-bright);
    color: var(--accent-green-bright);
    margin-top: 0.5rem;
}

@media (min-width: 500px) {
    .btn-secondary {
        margin-left: 0.5rem;
        margin-top: 0;
    }
}

.btn-secondary:hover {
    background-color: rgba(0, 176, 39, 0.1);
    color: var(--accent-green-bright);
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
}

.card h3 {
    color: var(--accent-green-bright);
    margin-bottom: 0.8rem;
    font-size: 1.2rem;
}

.calc-grid-full {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
}

.chart-container {
    background-color: var(--bg-dark);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1rem;
    position: relative;
    height: 300px;
    width: 100%;
}

@media (min-width: 768px) {
    .chart-container {
        height: 350px;
        padding: 1.5rem;
    }
}

.regression-stats {
    display: flex;
    gap: 1.5rem;
    background-color: var(--bg-dark);
    border: 1px solid var(--accent-green-bright);
    padding: 1rem;
    border-radius: 6px;
    margin-top: 1rem;
    font-size: 0.85rem;
    flex-wrap: wrap;
}

.regression-stats span {
    color: var(--accent-green-bright);
    font-weight: bold;
}

.file-drop-zone {
    border: 2px dashed var(--border-color);
    padding: 1.5rem;
    text-align: center;
    border-radius: 8px;
    background-color: var(--bg-dark);
    cursor: pointer;
    transition: border-color 0.2s;
    margin-bottom: 1.5rem;
}

.file-drop-zone:hover {
    border-color: var(--accent-green-bright);
}

.file-drop-zone input[type="file"] {
    display: none;
}

.data-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1rem;
    font-size: 0.85rem;
    min-width: 600px; /* Allows horizontal scrolling on small mobile screens */
}

.data-table th, .data-table td {
    border: 1px solid var(--border-color);
    padding: 0.5rem;
    text-align: left;
}

.data-table th {
    background-color: var(--bg-dark);
    color: var(--accent-green-bright);
}

.data-table tr:nth-child(even) {
    background-color: rgba(255, 255, 255, 0.02);
}

input, textarea, select {
    background-color: var(--bg-dark);
    border: 1px solid var(--border-color);
    padding: 0.6rem;
    color: var(--text-main);
    border-radius: 4px;
    font-size: 1rem; /* Prevents auto-zoom on iOS mobile browsers */
    width: 100%;
}

input:focus, textarea:focus, select:focus {
    outline: 1px solid var(--accent-green-bright);
}

.smiles-output-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-top: 1.5rem;
}

.stat-box {
    background-color: var(--bg-dark);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 1rem;
    text-align: center;
}

.stat-box .stat-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.stat-box .stat-value {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--accent-green-bright);
    margin-top: 0.3rem;
}

.structure-preview-box {
    background-color: var(--bg-dark);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1rem;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 220px;
    margin-top: 1.5rem;
    overflow: hidden;
}

.structure-preview-box svg {
    width: 100%;
    height: 100%;
    max-height: 220px;
}

form.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    max-width: 600px;
    margin: 0 auto;
}

.form-feedback {
    display: none;
    background-color: rgba(0, 176, 39, 0.15);
    border: 1px solid var(--accent-green-bright);
    color: var(--accent-green-bright);
    padding: 1rem;
    border-radius: 6px;
    text-align: center;
    max-width: 600px;
    margin: 0 auto 1.5rem;
}

footer {
    border-top: 1px solid var(--border-color);
    text-align: center;
    padding: 1.5rem;
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-top: auto;
}

/* --- Mobile Specific Media Queries --- */
@media (max-width: 768px) {
    .nav-container {
        padding: 0.8rem 1rem;
        flex-direction: column;
        align-items: flex-start;
    }

    nav ul {
        gap: 0.8rem;
        overflow-x: auto;
        width: 100%;
        padding-bottom: 0.5rem;
        flex-wrap: nowrap;
    }

    nav a {
        white-space: nowrap;
        font-size: 0.9rem;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 1rem;
    }

    .page-view {
        padding: 1.5rem 1rem;
    }

    .card {
        padding: 1.2rem;
    }
}