:root {
    --bg-color: #0f172a;
    --panel-bg: #1e293b;
    --border-color: #334155;
    --text-color: #f8fafc;
    --text-muted: #94a3b8;
    --accent-color: #3b82f6;
    --accent-hover: #60a5fa;
    --highlight-color: rgba(59, 130, 246, 0.2);
    --highlight-border: #3b82f6;
}

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
}

header {
    padding: 16px 24px;
    background-color: var(--panel-bg);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

footer {
    padding: 8px 24px;
    background-color: var(--panel-bg);
    border-top: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    color: var(--text-muted);
}

footer a {
    color: var(--accent-color);
    text-decoration: none;
    margin-left: 4px;
}

footer a:hover {
    text-decoration: underline;
}

h1 {
    margin: 0;
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.025em;
}

.main-container {
    display: flex;
    flex: 1;
    overflow: hidden;
}

.panel {
    background-color: var(--panel-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

#left-panel {
    width: 320px;
    min-width: 320px;
    padding: 20px;
    box-sizing: border-box;
    gap: 16px;
}

#center-panel {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: flex-start;
    background-color: #0b0f19;
}

#right-panel {
    width: 320px;
    min-width: 320px;
    border-right: none;
    border-left: 1px solid var(--border-color);
    padding: 20px;
    box-sizing: border-box;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-muted);
}

textarea {
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--text-color);
    border-radius: 6px;
    padding: 10px;
    font-family: monospace;
    font-size: 0.875rem;
    resize: vertical;
    min-height: 100px;
}

textarea:focus {
    outline: none;
    border-color: var(--accent-color);
}

button {
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 6px;
    padding: 10px 16px;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s;
}

button:hover {
    background-color: var(--accent-hover);
}

button:disabled {
    background-color: var(--border-color);
    color: var(--text-muted);
    cursor: not-allowed;
    opacity: 0.6;
}

#copy-btn:not(:disabled) {
    background-color: #10b981;
    color: white;
}

#copy-btn:not(:disabled):hover {
    background-color: #059669;
}

.section-title {
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    margin-bottom: 12px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 6px;
}

/* Slots Board (Center Panel) */
.board-container {
    display: flex;
    flex-direction: column;
    gap: 12px;
    width: 100%;
    max-width: 700px;
    margin-top: 10px;
}

.board-row {
    display: flex;
    align-items: center;
    padding: 10px 16px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--panel-bg);
    cursor: pointer;
    transition: all 0.2s;
    gap: 16px;
}

.board-row:hover {
    border-color: var(--text-muted);
}

.board-row.active {
    border-color: var(--accent-color);
    background-color: rgba(59, 130, 246, 0.05);
}

.board-row-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    width: 80px;
    min-width: 80px;
    font-weight: 500;
}

.board-row-inputs {
    display: flex;
    gap: 8px;
    flex: 1;
    flex-wrap: wrap;
}

.cell-square {
    position: relative;
    width: 44px;
    height: 44px;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-sizing: border-box;
    transition: all 0.2s;
}

.cell-square:focus-within {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.2);
}

.cell-square.crossing-highlight {
    border-color: #eab308; /* yellow accent for crossing cells */
    background-color: rgba(234, 179, 8, 0.15);
}

.cell-square-name {
    position: absolute;
    top: 2px;
    left: 4px;
    font-size: 0.55rem;
    color: var(--text-muted);
    text-transform: uppercase;
    pointer-events: none;
}

.cell-square-input {
    width: 100%;
    height: 100%;
    border: none;
    background: transparent;
    color: var(--text-color);
    font-size: 1.25rem;
    font-weight: 750;
    text-align: center;
    text-transform: uppercase;
    padding-top: 10px;
    box-sizing: border-box;
}

.cell-square-input:focus {
    outline: none;
}

/* Slots List */
.slots-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
    overflow-y: auto;
    flex: 1;
}

.slot-item {
    padding: 8px 12px;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-color);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all 0.2s;
}

.slot-item:hover {
    border-color: var(--text-muted);
}

.slot-item.active {
    border-color: var(--accent-color);
    background-color: var(--highlight-color);
}

.slot-name {
    font-family: monospace;
    font-size: 0.9rem;
}

.slot-length {
    font-size: 0.75rem;
    color: var(--text-muted);
    background-color: var(--panel-bg);
    padding: 2px 6px;
    border-radius: 4px;
}

/* Candidates list */
.candidates-container {
    display: flex;
    flex-direction: column;
    flex: 1;
    overflow-y: auto;
}

.candidates-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.candidate-item {
    padding: 8px 12px;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    cursor: pointer;
    font-family: monospace;
    font-size: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all 0.2s;
}

.candidate-item.pending {
    color: var(--text-muted);
    opacity: 0.65;
}

.candidate-item.valid {
    color: var(--text-color);
    font-weight: 600;
    border-color: #3b82f6;
    background-color: rgba(59, 130, 246, 0.05);
}

.candidate-item:hover {
    border-color: var(--accent-hover);
    background-color: var(--highlight-color);
}

.no-candidates {
    color: var(--text-muted);
    font-size: 0.875rem;
    text-align: center;
    margin-top: 20px;
}

/* Modal Settings styles */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease;
}

.modal-overlay.open {
    opacity: 1;
    pointer-events: auto;
}

.modal-card {
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    width: 90%;
    max-width: 550px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    animation: modalSlide 0.2s ease;
}

@keyframes modalSlide {
    from { transform: translateY(20px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

.modal-header {
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h2 {
    margin: 0;
    font-size: 1.1rem;
    font-weight: 600;
}

.modal-close-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.25rem;
    cursor: pointer;
    padding: 4px;
    line-height: 1;
    transition: color 0.2s;
}

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

.modal-body {
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 16px;
    max-height: 70vh;
    overflow-y: auto;
}

.modal-footer {
    padding: 16px 20px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: flex-end;
    gap: 12px;
    background-color: rgba(0, 0, 0, 0.1);
}

/* Active Config card on left panel */
.active-config-card {
    background-color: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 14px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-bottom: 16px;
}

.active-config-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
}

.active-config-value {
    font-weight: 500;
    color: var(--text-color);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    max-width: 160px;
}

/* Modal Tabs styles */
.modal-tabs {
    display: flex;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 16px;
    gap: 8px;
}
.modal-tab-btn {
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-muted);
    border-radius: 0;
    padding: 8px 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}
.modal-tab-btn:hover {
    color: var(--text-color);
    background: transparent;
}
.modal-tab-btn.active {
    color: var(--accent-color);
    border-bottom-color: var(--accent-color);
    background: transparent;
}
.tab-content {
    display: none;
}
.tab-content.active {
    display: flex;
    flex-direction: column;
    gap: 16px;
}