:root {
    /* Deep violet/blue dark theme */
    --bg-base: #0f111a;
    --bg-panel: #1a1d2d;
    --bg-surface: #24283b;
    
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    
    --border: #3b4261;
    --border-light: rgba(59, 66, 97, 0.5);
    
    --primary: #7aa2f7;
    --primary-hover: #89b4fc;
    
    --accent: #bb9af7;
    
    --success: #9ece6a;
    --error: #f7768e;
    --warning: #e0af68;
    
    --radius: 12px;
    --radius-sm: 8px;
    
    --shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -4px rgba(0, 0, 0, 0.5);
    
    /* Glassmorphism */
    --glass-bg: rgba(26, 29, 45, 0.7);
    --glass-border: rgba(255, 255, 255, 0.05);
}

[data-theme="light"] {
    --bg-base: #f1f5f9;
    --bg-panel: #ffffff;
    --bg-surface: #f8fafc;
    
    --text-main: #0f172a;
    --text-muted: #64748B;
    
    --border: #e2e8f0;
    --border-light: rgba(15, 23, 42, 0.05);
    
    --primary: #3b82f6;
    --primary-hover: #2563eb;
    
    --accent: #8b5cf6;
    
    --success: #10b981;
    --error: #ef4444;
    --warning: #f59e0b;
    
    --shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.05);
    
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(0, 0, 0, 0.05);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color 0.3s ease, border-color 0.3s ease, color 0.3s ease;
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-base);
    color: var(--text-main);
    line-height: 1.5;
    min-height: 100vh;
    overflow-x: hidden;
}

/* Typography elements */
h1, h2, h3, h4 { font-weight: 600; color: var(--text-main); }
.text-muted { color: var(--text-muted); }
.text-sm { font-size: 0.85rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-4 { margin-top: 1rem; }
.w-full { width: 100%; }

code {
    font-family: 'Fira Code', monospace;
    background-color: var(--bg-surface);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-size: 0.85em;
    color: var(--accent);
}

/* Layout */
.app-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    max-width: 1200px;
    margin: 0 auto;
    padding: 1.5rem;
    gap: 1.5rem;
}

/* Header */
.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    padding: 1rem 1.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.brand {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.logo-box {
    width: 44px;
    height: 44px;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    box-shadow: 0 4px 10px rgba(139, 92, 246, 0.3);
}

.brand h1 {
    font-size: 1.25rem;
    letter-spacing: -0.02em;
    line-height: 1.2;
}

.brand-subtitle {
    font-size: 0.8rem;
    color: var(--accent);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.header-nav {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    font-weight: 500;
    font-size: 0.95rem;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-family: inherit;
    transition: all 0.2s;
}
.nav-btn i { width: 18px; height: 18px; }
.nav-btn:hover {
    color: var(--text-main);
    background: var(--bg-surface);
}
.nav-btn.active {
    color: var(--primary);
    background: rgba(122, 162, 247, 0.1);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.6rem 1.2rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    border: 1px solid transparent;
    font-family: inherit;
    transition: all 0.2s;
}
.btn i { width: 18px; height: 18px; }
.btn-sm { padding: 0.4rem 0.8rem; font-size: 0.85rem; }
.btn-icon { padding: 0.5rem; border-radius: 8px; background: transparent; color: var(--text-muted); border-color: var(--border); }
.btn-icon:hover { background-color: var(--bg-surface); color: var(--text-main); }

.btn-primary { background: linear-gradient(135deg, var(--primary), var(--accent)); color: white; border: none; }
.btn-primary:hover { opacity: 0.9; transform: translateY(-1px); box-shadow: 0 4px 12px rgba(122, 162, 247, 0.4); }
.btn-secondary { background: var(--bg-surface); color: var(--text-main); border-color: var(--border); }
.btn-secondary:hover { border-color: var(--primary); color: var(--primary); }
.btn-outline { background: transparent; color: var(--text-main); border-color: var(--border); }
.btn-outline:hover { background: var(--bg-surface); border-color: var(--text-muted); }

/* Main Views */
.main-content {
    flex: 1;
    position: relative;
}

.view-section {
    display: none;
    animation: fadeIn 0.4s ease forwards;
}
.view-section.active { display: block; }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.layout-grid {
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 1.5rem;
}

@media (max-width: 900px) {
    .layout-grid { grid-template-columns: 1fr; }
}

/* Panels */
.panel {
    background-color: var(--bg-panel);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    position: relative;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border);
    background-color: var(--bg-surface);
}

.panel-header h2 { font-size: 1.1rem; }
.panel-body { padding: 1.5rem; }

/* Game / Crossword Grid */
.puzzle-container {
    padding: 2rem;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: auto;
    min-height: 400px;
    background-image: radial-gradient(var(--border) 1px, transparent 1px);
    background-size: 20px 20px;
}

.crossword-wrapper {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.crossword-body {
    display: flex;
    gap: 10px;
}

/* Hints layout */
.hints-row, .hints-col {
    display: flex;
    gap: 8px;
    font-family: 'Fira Code', monospace;
    font-size: 0.9rem;
    font-weight: 500;
}
.hints-row {
    flex-direction: row;
    justify-content: space-evenly;
    margin-left: 140px; /* offset for left hints column */
}
.hints-col {
    flex-direction: column;
    justify-content: space-evenly;
    align-items: flex-end;
    width: 130px;
}

/* Common hint boxes */
.hint-box {
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--bg-base);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--accent);
    padding: 0.5rem;
    text-align: center;
    white-space: pre;
    transition: all 0.2s;
    user-select: none;
}
.hint-box.valid { border-color: var(--success); color: var(--success); background-color: rgba(158, 206, 106, 0.1); }
.hint-box.invalid { border-color: var(--error); color: var(--error); background-color: rgba(247, 118, 142, 0.1); }

.top-hints .hint-box { width: 50px; min-height: 60px; writing-mode: vertical-rl; transform: rotate(180deg); }
.left-hints .hint-box { height: 50px; min-width: 100px; padding: 0 0.75rem; justify-content: flex-end; }

/* Grid Container */
.grid-container {
    display: grid;
    gap: 8px;
}

.grid-cell {
    width: 50px;
    height: 50px;
    background-color: var(--bg-surface);
    border: 2px solid var(--border);
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary);
    text-transform: uppercase;
    cursor: pointer;
    transition: all 0.15s;
    outline: none;
    caret-color: transparent; /* hide native caret */
}
.grid-cell:focus { border-color: var(--primary); box-shadow: 0 0 0 3px rgba(122, 162, 247, 0.2); }
.grid-cell.correct-anim { animation: pulseSuccess 0.5s ease; }
@keyframes pulseSuccess {
    0% { transform: scale(1); border-color: var(--border); }
    50% { transform: scale(1.1); border-color: var(--success); background-color: rgba(158, 206, 106, 0.2); color: var(--success); }
    100% { transform: scale(1); border-color: var(--border); }
}

/* Level List */
.level-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}
.level-item {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-sm);
    background-color: var(--bg-surface);
    border: 1px solid var(--border);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
    transition: all 0.2s;
}
.level-item:hover { border-color: var(--text-muted); }
.level-item.active { border-color: var(--primary); background: rgba(122, 162, 247, 0.1); }
.level-meta { font-size: 0.75rem; color: var(--text-muted); }
.level-status i { color: var(--success); display: none; }
.level-item.completed .level-status i { display: block; }

/* Regex Cheat Sheet */
.cheat-sheet {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}
.cheat-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 0.85rem;
    color: var(--text-muted);
}
.cheat-item code { min-width: 60px; text-align: center; }

/* Validation Msg */
.validation-message {
    padding: 1rem 1.5rem;
    text-align: center;
    font-weight: 500;
    border-top: 1px solid var(--border);
    display: none;
}
.validation-message.success { display: block; background: rgba(158, 206, 106, 0.1); color: var(--success); border-top-color: rgba(158, 206, 106, 0.3); }

/* CREATE MODE styles */
.create-panel .panel-body { padding: 2rem; }
.setup-controls { display: flex; gap: 1rem; align-items: flex-end; }
.input-group { display: flex; flex-direction: column; gap: 0.4rem; }
.input-group label { font-size: 0.85rem; font-weight: 500; color: var(--text-muted); }
.form-control {
    background-color: var(--bg-surface);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius-sm);
    font-family: inherit;
    outline: none;
}
.form-control:focus { border-color: var(--primary); }

.workspace-step { margin-bottom: 2rem; padding-bottom: 1.5rem; border-bottom: 1px solid var(--border-light); }
.workspace-step:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }
.workspace-step h3 { margin-bottom: 0.25rem; font-size: 1.1rem; color: var(--primary); }
.create-workspace .grid-container {
    margin-top: 1rem;
    justify-content: center;
}

.constraints-editor {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    margin-top: 1rem;
}
.constraint-group h4 {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}
.constraint-input {
    display: flex;
    align-items: center;
    margin-bottom: 0.5rem;
    gap: 0.5rem;
}
.constraint-input label {
    font-family: 'Fira Code', monospace;
    font-weight: 600;
    color: var(--accent);
    min-width: 24px;
}
.constraint-input input {
    flex: 1;
    font-family: 'Fira Code', monospace;
    font-size: 0.9rem;
}

.create-actions { display: flex; gap: 1rem; justify-content: flex-end; border-top: 1px solid var(--border); padding-top: 1.5rem; }

.info-list { padding-left: 1.5rem; margin-top: 0.75rem; font-size: 0.9rem; color: var(--text-muted); line-height: 1.6; }
.info-list li { margin-bottom: 0.5rem; }

/* Toast */
.toast {
    position: fixed;
    bottom: 2rem; left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--text-main);
    color: var(--bg-base);
    padding: 0.75rem 1.5rem;
    border-radius: 30px;
    font-size: 0.9rem;
    font-weight: 600;
    box-shadow: 0 10px 25px rgba(0,0,0,0.5);
    opacity: 0;
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    z-index: 2000;
    pointer-events: none;
}
.toast.show { transform: translateX(-50%) translateY(0); opacity: 1; }