:root {
    /* Mapping local vars to global theme */
    --border-color: rgba(255, 255, 255, 0.2);
    --text-color: var(--text-main);
    --primary-color: var(--accent-color);
    --secondary-color: var(--text-muted);
    --prime-color: var(--tag-bg-green);
    --not-prime-color: var(--tag-bg-red);
    --table-header-bg: rgba(255, 255, 255, 0.05);
    --cell-empty-bg: transparent;
    --bg-color: var(--bg-dark);
}

/* --- Modal Styles (Kept) --- */
.modal-toggle {
    display: none;
}

.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.75);
    z-index: 2000;
    /* Higher than nav */
    display: flex;
    justify-content: center;
    align-items: center;
    visibility: hidden;
    opacity: 0;
    transition: visibility 0s 0.2s, opacity 0.2s ease-in-out;
}

.modal-content {
    position: relative;
    background: var(--card-bg);
    /* Use main theme var */
    padding: 2rem 2.5rem;
    border-radius: 16px;
    border: 1px solid var(--card-border);
    backdrop-filter: blur(12px);
    width: 90%;
    max-width: 600px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    color: var(--text-main);
}

.modal-close {
    position: absolute;
    top: 10px;
    right: 15px;
    font-size: 2rem;
    font-weight: bold;
    color: var(--text-muted);
    cursor: pointer;
    line-height: 1;
    transition: color 0.2s;
}

.modal-close:hover {
    color: var(--accent-color);
}

.modal-toggle:checked~.modal-overlay {
    visibility: visible;
    opacity: 1;
    transition: opacity 0.2s ease-in-out;
}

.modal-content h3 {
    color: var(--accent-color);
    margin-top: 0;
    border-bottom: 1px solid var(--card-border);
    padding-bottom: 0.5rem;
}

.modal-content p,
.modal-content ul {
    line-height: 1.6;
    opacity: 0.9;
}

.modal-content ul {
    padding-left: 20px;
}

.modal-content li {
    margin-bottom: 0.5rem;
}

/* --- App Container --- */
.app-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    width: 100%;
    max-width: 1000px;
    margin: 0 auto;
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    margin-bottom: -1rem;
}

.help-icon {
    display: inline-block;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    border: 2px solid var(--text-color);
    text-align: center;
    line-height: 24px;
    font-weight: bold;
    cursor: pointer;
    user-select: none;
    transition: background-color 0.2s, color 0.2s;
}

.help-icon:hover {
    background-color: var(--primary-color);
    color: var(--bg-color);
    border-color: var(--primary-color);
}

h1 {
    color: var(--primary-color);
    margin: 0;
}

.controls {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

#prime-indicator {
    margin: 0;
    height: 1.2rem;
    font-style: italic;
    font-weight: bold;
    font-size: 1.1rem;
}

.is-prime {
    color: var(--prime-color);
}

.is-not-prime {
    color: var(--not-prime-color);
}

input[type="number"] {
    background-color: #333;
    color: var(--text-color);
    border: 1px solid var(--border-color);
    padding: 8px 12px;
    border-radius: 5px;
    font-size: 1.1rem;
    text-align: center;
    width: 150px;
}

canvas {
    border: 2px solid var(--border-color);
    background-color: #2b2b2b;
    border-radius: 5px;
    cursor: crosshair;
}

.results {
    width: 100%;
    text-align: center;
}

h2 {
    color: var(--secondary-color);
    font-size: 1.2rem;
}

.results>p {
    margin-top: -10px;
    font-size: 0.9rem;
    opacity: 0.8;
}

#grid-container {
    width: 100%;
    overflow-x: auto;
}

table {
    border-collapse: collapse;
    margin-top: 1rem;
    font-size: 0.85rem;
    font-family: "Courier New", Courier, monospace;
}

th,
td {
    border: 1px solid var(--border-color);
    padding: 8px;
    text-align: center;
    min-width: 90px;
    height: 50px;
    transition: background-color 0.2s ease;
}

th {
    background-color: var(--table-header-bg);
    color: var(--primary-color);
    font-weight: bold;
}

td {
    background-color: var(--cell-empty-bg);
}

td:not(:empty) {
    background-color: #333;
    color: var(--accent-color);
    font-weight: bold;
}

thead th:first-child {
    background-color: #111;
    color: var(--text-color);
}

td.highlight {
    background-color: #505030;
    outline: 2px solid var(--accent-color);
    outline-offset: -2px;
}