:root {
    --primary: #00CEC9;
    --secondary: #FDCB6E;
    --bg: #1A1A2E;
    --bg-panel: rgba(26, 26, 46, 0.92);
    --border: rgba(255, 255, 255, 0.08);
    --text: #E8E8F0;
    --text-muted: #8E8EA0;
    --cell-bg: rgba(0, 0, 0, 0.3);
    --cell-correct: rgba(0, 206, 201, 0.15);
    --cell-wrong: rgba(239, 68, 68, 0.15);
    --radius: 10px;
    --transition: all 0.2s ease;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', system-ui, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    background: radial-gradient(circle at top, rgba(0, 206, 201, 0.06), transparent 50%),
        radial-gradient(circle at bottom right, rgba(253, 203, 110, 0.04), transparent 50%),
        var(--bg);
}

.app {
    width: 100%;
    max-width: 1100px;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.glass-panel {
    background: var(--bg-panel);
    backdrop-filter: blur(16px);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
    padding: 1.25rem;
}

header {
    padding: 0.75rem 1.25rem;
}

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

.header-right {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

h1 {
    font-size: 1.4rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.timer {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1rem;
    color: var(--secondary);
}

select {
    padding: 0.35rem 0.5rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: rgba(0, 0, 0, 0.3);
    color: var(--text);
    font-family: 'Inter', sans-serif;
    font-size: 0.8rem;
}

.layout {
    display: grid;
    grid-template-columns: 1fr 260px;
    gap: 1.25rem;
}

/* Puzzle header */
.puzzle-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

h2 {
    font-size: 1.05rem;
    font-weight: 600;
}

.puzzle-meta {
    display: flex;
    gap: 0.5rem;
    align-items: center;
    margin-top: 0.2rem;
}

.badge {
    font-size: 0.7rem;
    background: rgba(0, 206, 201, 0.15);
    color: var(--primary);
    padding: 0.15rem 0.5rem;
    border-radius: 12px;
}

.stars {
    font-size: 0.9rem;
}

.puzzle-actions {
    display: flex;
    gap: 0.4rem;
}

.btn-sm {
    padding: 0.3rem 0.6rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: transparent;
    color: var(--text-muted);
    font-size: 0.75rem;
    cursor: pointer;
    transition: var(--transition);
    font-family: 'Inter', sans-serif;
}

.btn-sm:hover {
    border-color: var(--primary);
    color: var(--primary);
}

/* Grid */
.grid-area {
    display: flex;
    gap: 0;
    margin-top: 0.5rem;
}

.row-labels {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding-right: 0.5rem;
}

.row-label {
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--primary);
    padding-right: 0.3rem;
}

.col-labels {
    display: flex;
    padding-left: 0;
    margin-left: auto;
    gap: 2px;
    margin-bottom: 0.3rem;
}

.col-label {
    width: 44px;
    text-align: center;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--primary);
    transform: rotate(-30deg);
    transform-origin: bottom center;
    height: 40px;
    display: flex;
    align-items: flex-end;
    justify-content: center;
}

.grid {
    display: grid;
    gap: 2px;
}

.cell {
    width: 44px;
    height: 44px;
    border: 1px solid var(--border);
    border-radius: 4px;
    background: var(--cell-bg);
    color: var(--text);
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.1rem;
    text-align: center;
    text-transform: uppercase;
    transition: var(--transition);
    cursor: text;
}

.cell:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(0, 206, 201, 0.2);
}

.cell.correct {
    background: var(--cell-correct);
    border-color: var(--primary);
}

.cell.wrong {
    background: var(--cell-wrong);
    border-color: #EF4444;
}

.cell.hinted {
    color: var(--secondary);
}

.feedback {
    text-align: center;
    padding: 0.5rem;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.9rem;
    margin-top: 0.5rem;
}

.feedback.success {
    background: rgba(0, 206, 201, 0.15);
    color: var(--primary);
}

.feedback.error {
    background: rgba(239, 68, 68, 0.1);
    color: #EF4444;
}

.hidden {
    display: none !important;
}

.hints-used {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 0.3rem;
}

/* Sidebar */
.sidebar h2 {
    font-size: 0.95rem;
    margin-bottom: 0.5rem;
    border-bottom: 1px solid var(--border);
    padding-bottom: 0.4rem;
}

.sidebar h3 {
    font-size: 0.85rem;
    margin: 0.75rem 0 0.4rem;
    color: var(--text-muted);
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 3px;
    transition: width 0.3s;
}

.progress-text {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 0.2rem;
}

.puzzle-list {
    max-height: 200px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}

.puzzle-list-item {
    padding: 0.3rem 0.5rem;
    border-radius: 4px;
    font-size: 0.78rem;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.puzzle-list-item:hover {
    background: rgba(0, 206, 201, 0.08);
}

.puzzle-list-item.active {
    background: rgba(0, 206, 201, 0.15);
    color: var(--primary);
}

.puzzle-list-item.completed {
    opacity: 0.6;
}

.puzzle-list-item .checkmark {
    color: var(--primary);
}

.tutorial-notes {
    font-size: 0.78rem;
    line-height: 1.8;
}

.tutorial-notes code {
    font-family: 'JetBrains Mono', monospace;
    color: var(--primary);
    background: rgba(0, 206, 201, 0.08);
    padding: 0.05rem 0.25rem;
    border-radius: 3px;
}

footer {
    padding: 0.75rem;
    text-align: center;
    font-size: 0.75rem;
    color: var(--text-muted);
}

@media (max-width: 768px) {
    .layout {
        grid-template-columns: 1fr;
    }
}