:root {
    --board-max-width: 500px;
    --cell-font-size: 28px;
    --grid-border-width: 5px;
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background-color 0.3s ease;
    overflow-x: hidden;
    -webkit-tap-highlight-color: transparent;
}

#grid {
    width: 100%;
    max-width: var(--board-max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 1px;
    background-color: var(--grid-strong);
    border: var(--grid-border-width) solid var(--grid-strong);
    border-radius: 0;
    overflow: hidden;
    box-shadow: 0 20px 40px -10px rgba(0, 0, 0, 0.3);
}

.sudoku-cell {
    aspect-ratio: 1 / 1;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    user-select: none;
    position: relative;
    font-size: var(--cell-font-size);
    background-color: var(--cell-bg);
    transition: background-color 0.1s ease;
    box-sizing: border-box;
}

/* 3x3 Grid Indicators - Matching outer border thickness */
.sudoku-cell:nth-child(3n):not(:nth-child(9n))::before {
    content: '';
    position: absolute;
    top: 0;
    bottom: 0;
    right: calc(var(--grid-border-width) * -0.5);
    width: var(--grid-border-width);
    background-color: var(--grid-strong);
    z-index: 5;
    pointer-events: none;
}

.sudoku-cell:nth-child(n+19):nth-child(-n+27)::after,
.sudoku-cell:nth-child(n+46):nth-child(-n+54)::after {
    content: '';
    position: absolute;
    left: 0;
    right: 0;
    bottom: calc(var(--grid-border-width) * -0.5);
    height: var(--grid-border-width);
    background-color: var(--grid-strong);
    z-index: 5;
    pointer-events: none;
}

.num-completed {
    opacity: 0.1 !important;
    filter: grayscale(1) brightness(0.5);
    pointer-events: none !important;
    box-shadow: none !important;
}

/* Numpad Styling for per-number pins */
.numpad-item {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.btn-numpad {
    width: 100%;
    background: var(--card-bg);
    border: 1px solid var(--cell-border);
    color: var(--text-primary);
    padding: 10px 0;
    border-radius: 10px;
    font-weight: 800;
    font-size: 1.1rem;
    transition: all 0.1s;
}

.btn-pin-mini {
    width: 100%;
    background: rgba(255,255,255,0.03);
    border: 1px solid var(--cell-border);
    color: var(--text-secondary);
    font-size: 8px;
    padding: 4px 0;
    border-radius: 6px;
    transition: all 0.1s;
    opacity: 0.4;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 3px;
}

.pin-count {
    font-weight: 800;
    font-size: 7px;
    opacity: 0.8;
}

.pin-active {
    background: var(--accent) !important;
    color: white !important;
    opacity: 1 !important;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.cell-active { 
    background-color: var(--cell-active) !important; 
    box-shadow: inset 0 0 0 2px var(--accent) !important;
    z-index: 10;
}

.cell-highlight { 
    background-color: var(--cell-highlight); 
}

.cell-same-num { 
    background-color: var(--cell-same-num) !important;
}

.cell-fixed { 
    color: var(--cell-fixed); 
    font-weight: 700; 
}

.cell-user { 
    color: var(--cell-user); 
    font-weight: 700; 
}

.cell-error { 
    color: #ef4444 !important; 
    font-weight: 800 !important;
    background-color: transparent !important;
    box-shadow: none !important;
    animation: shake 0.3s ease-in-out;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-2px); }
    75% { transform: translateX(2px); }
}

.glass {
    background: var(--card-bg);
    border: 1px solid var(--cell-border);
}

.btn-glass {
    background: var(--card-bg);
    border: 1px solid var(--cell-border);
    color: var(--text-primary);
    transition: all 0.1s;
}
.btn-glass:hover {
    background: var(--cell-highlight);
}

.progress-bar {
    height: 6px;
    background: var(--cell-border);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent);
    transition: width 0.3s ease;
}

.modal-overlay {
    position: fixed;
    inset: 0;
    background: var(--modal-bg);
    backdrop-filter: blur(12px);
    z-index: 1000;
    display: none;
    align-items: flex-start;
    justify-content: center;
    opacity: 0;
    transition: opacity 0.3s ease;
    overflow-y: auto;
    padding: 2rem 1rem;
}
.modal-overlay.active { display: flex; opacity: 1; }

.btn-active {
    background: var(--accent) !important;
    color: white !important;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.2);
}

.note-grid {
    display: grid !important;
    grid-template-columns: repeat(3, 1fr) !important;
    grid-template-rows: repeat(3, 1fr) !important;
    position: absolute;
    inset: 0;
    padding: 4px;
    pointer-events: none;
    font-size: 9px !important;
    line-height: 1 !important;
    color: var(--text-secondary);
    font-weight: 300 !important;
    opacity: 0.7;
}

.note-grid div {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    width: 100%;
}

/* Ghost Hint Styling */
.ghost-hint {
    opacity: 0.35;
    transition: opacity 0.5s ease-in-out;
    filter: blur(0.3px);
}

/* New Footer Styles */
.footer-link {
    font-size: 10px;
    font-weight: 600;
    opacity: 0.4;
    transition: all 0.2s;
    cursor: pointer;
}
.footer-link:hover {
    opacity: 1;
    color: var(--accent);
}

/* Range Sliders visibility */
input[type="range"] {
    background: rgba(128, 128, 128, 0.2) !important;
}

input[type="range"]::-webkit-slider-runnable-track {
    background: transparent;
}

/* Custom Toggle Knob */
#ghost-hint-knob {
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}