:root {
    --bg-dark: #0a0a1a;
    --glass-bg: rgba(255, 255, 255, 0.03);
    --glass-border: rgba(255, 255, 255, 0.1);
    --neon-cyan: #00f3ff;
    --neon-purple: #9d00ff;
    --neon-pink: #ff00ea;
    
    --cell-size: clamp(30px, 8vw, 45px);
    --board-gap: 2px;
    --box-gap: 6px;
    
    --text-main: #ffffff;
    --text-dim: rgba(255, 255, 255, 0.6);
    --text-fixed: #00f3ff;
    --text-error: #ff3366;
    
    --cell-bg: rgba(255, 255, 255, 0.05);
    --cell-bg-hover: rgba(255, 255, 255, 0.15);
    --cell-bg-selected: rgba(0, 243, 255, 0.2);
    --cell-bg-highlight: rgba(255, 255, 255, 0.1);
    --cell-bg-error: rgba(255, 51, 102, 0.2);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Outfit', sans-serif;
}

body {
    background-color: var(--bg-dark);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    position: relative;
}

/* Background Animated Blobs */
.background-elements {
    position: absolute;
    top: 0; left: 0; width: 100%; height: 100%;
    z-index: -1;
    overflow: hidden;
}

.blob {
    position: absolute;
    border-radius: 50%;
    filter: blur(80px);
    opacity: 0.6;
    animation: float 20s infinite alternate;
}

.blob-1 {
    width: 40vw; height: 40vw;
    background: radial-gradient(circle, var(--neon-purple), transparent 70%);
    top: -10%; left: -10%;
}

.blob-2 {
    width: 35vw; height: 35vw;
    background: radial-gradient(circle, var(--neon-cyan), transparent 70%);
    bottom: -10%; right: -10%;
    animation-delay: -5s;
}

.blob-3 {
    width: 30vw; height: 30vw;
    background: radial-gradient(circle, var(--neon-pink), transparent 70%);
    top: 40%; left: 60%;
    animation-delay: -10s;
}

@keyframes float {
    0% { transform: translate(0, 0) scale(1); }
    100% { transform: translate(10%, 10%) scale(1.1); }
}

/* Glass Container */
.glass-container {
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: 24px;
    padding: 2rem;
    box-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    z-index: 10;
    width: 95vw;
    max-width: 500px;
    animation: fadeIn 1s ease-out;
}

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

header {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    text-align: center;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: 2px;
}

.neon-text {
    color: var(--neon-cyan);
    text-shadow: 0 0 10px var(--neon-cyan);
}

.controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.stats {
    display: flex;
    justify-content: space-between;
    font-size: 1.2rem;
    font-weight: 300;
    color: var(--text-dim);
}

/* Buttons and Selects */
.glow-btn {
    background: transparent;
    color: var(--neon-cyan);
    border: 1px solid var(--neon-cyan);
    padding: 0.5rem 1rem;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.glow-btn:hover {
    background: var(--neon-cyan);
    color: var(--bg-dark);
    box-shadow: 0 0 15px var(--neon-cyan);
    transform: translateY(-2px);
}

.glass-select {
    background: rgba(0,0,0,0.5);
    color: white;
    border: 1px solid var(--glass-border);
    padding: 0.5rem;
    border-radius: 8px;
    outline: none;
    font-family: inherit;
    cursor: pointer;
}

.glass-select option {
    background: var(--bg-dark);
}

/* Board */
main {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    align-items: center;
}

.board {
    display: grid;
    grid-template-columns: repeat(9, var(--cell-size));
    grid-template-rows: repeat(9, var(--cell-size));
    gap: var(--board-gap);
    background: var(--glass-border);
    padding: var(--board-gap);
    border-radius: 8px;
    /* Box separation */
    border: 2px solid var(--neon-purple);
    box-shadow: 0 0 15px rgba(157, 0, 255, 0.3);
}

.cell {
    background: var(--cell-bg);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: calc(var(--cell-size) * 0.5);
    font-weight: 400;
    cursor: pointer;
    transition: all 0.2s ease;
    user-select: none;
    color: var(--text-main);
}

/* Thicker borders for 3x3 boxes */
.cell:nth-child(3n) { margin-right: var(--box-gap); }
.cell:nth-child(9n) { margin-right: 0; }
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) { margin-bottom: var(--box-gap); }

.cell:hover {
    background: var(--cell-bg-hover);
    transform: scale(1.05);
    z-index: 2;
    box-shadow: 0 0 10px rgba(255,255,255,0.2);
    border-radius: 4px;
}

.cell.selected {
    background: var(--cell-bg-selected);
    border: 2px solid var(--neon-cyan);
    box-shadow: inset 0 0 10px rgba(0, 243, 255, 0.5);
    border-radius: 4px;
}

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

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

.cell.error {
    color: var(--text-error);
    background: var(--cell-bg-error);
    animation: shake 0.4s cubic-bezier(.36,.07,.19,.97) both;
}

@keyframes shake {
    10%, 90% { transform: translate3d(-1px, 0, 0); }
    20%, 80% { transform: translate3d(2px, 0, 0); }
    30%, 50%, 70% { transform: translate3d(-4px, 0, 0); }
    40%, 60% { transform: translate3d(4px, 0, 0); }
}

.cell.pop {
    animation: pop 0.3s ease-out;
}

@keyframes pop {
    0% { transform: scale(1); }
    50% { transform: scale(1.2); }
    100% { transform: scale(1); }
}

/* Numpad */
.numpad {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 8px;
    width: 100%;
}

.num-btn {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 10px 0;
    border-radius: 8px;
    font-size: 1.2rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.num-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
    border-color: var(--neon-purple);
    box-shadow: 0 0 10px rgba(157, 0, 255, 0.4);
}

.action-buttons {
    display: flex;
    gap: 1rem;
    width: 100%;
}

.action-btn {
    flex: 1;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 10px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
    text-transform: uppercase;
    font-size: 0.9rem;
    letter-spacing: 1px;
}

.action-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--text-main);
}

/* Modals */
.modal {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.8);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 100;
    opacity: 1;
    transition: opacity 0.3s ease;
}

.modal.hidden {
    opacity: 0;
    pointer-events: none;
}

.glass-panel {
    background: rgba(10, 10, 26, 0.7);
    backdrop-filter: blur(20px);
    border: 1px solid var(--neon-cyan);
    box-shadow: 0 0 30px rgba(0, 243, 255, 0.2);
    padding: 3rem;
    border-radius: 20px;
    text-align: center;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    transform: scale(1);
    transition: transform 0.3s ease;
}

.modal.hidden .glass-panel {
    transform: scale(0.8);
}

.glass-panel h2 {
    font-size: 3rem;
    color: var(--neon-cyan);
    text-shadow: 0 0 10px var(--neon-cyan);
}

/* Confetti specific */
.confetti {
    position: absolute;
    width: 10px;
    height: 10px;
    background-color: #f00;
    pointer-events: none;
    z-index: 90;
}

/* Screen visibility */
.glass-container.hidden {
    display: none !important;
}

/* Home Screen */
.home-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2rem;
    padding: 2rem 0;
}

.main-title {
    font-size: 3.5rem;
    font-weight: 700;
    letter-spacing: 3px;
    text-align: center;
}

.subtitle {
    color: var(--text-dim);
    font-size: 1.2rem;
    font-weight: 300;
}

.home-diff {
    width: 100%;
    max-width: 250px;
}

.setup-group {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    width: 100%;
    max-width: 250px;
}

.glass-input {
    background: rgba(0,0,0,0.5);
    color: white;
    border: 1px solid var(--glass-border);
    padding: 0.8rem;
    border-radius: 8px;
    outline: none;
    font-family: inherit;
    font-size: 1.2rem;
    text-align: center;
    width: 100%;
    transition: all 0.3s ease;
}

.glass-input:focus {
    border-color: var(--neon-cyan);
    box-shadow: 0 0 10px rgba(0, 243, 255, 0.3);
}

.leaderboard-container {
    margin-top: 2rem;
    width: 100%;
    background: rgba(255,255,255,0.02);
    border: 1px solid var(--glass-border);
    border-radius: 12px;
    padding: 1.5rem;
}

.lb-title {
    color: var(--neon-pink);
    margin-bottom: 1rem;
    text-align: center;
    font-size: 1.5rem;
    letter-spacing: 2px;
}

.leaderboard-grid {
    display: grid;
    grid-template-columns: 1.2fr 1.5fr 1.2fr 1fr;
    gap: 0.8rem 0.5rem;
    font-size: 1.1rem;
    text-align: center;
    align-items: center;
}

.lb-header {
    color: var(--text-dim);
    font-weight: 300;
    font-size: 0.9rem;
    border-bottom: 1px solid var(--glass-border);
    padding-bottom: 0.5rem;
}

.lb-mode {
    color: var(--neon-purple);
    font-weight: 600;
}

.home-diff select {
    width: 100%;
    font-size: 1.2rem;
    padding: 0.8rem;
    text-align: center;
}

.start-btn {
    font-size: 1.5rem;
    padding: 1rem 3rem;
    margin-top: 1rem;
    background: rgba(0, 243, 255, 0.1);
}

.score-display {
    font-size: 1.5rem;
    font-weight: 600;
}