:root {
    --bg-color: #f4f7f6;
    --card-bg: #ffffff;
    --text-main: #2c3e50;
    --text-muted: #7f8c8d;
    --primary: #3498db;
    --success: #2ecc71;
    --error: #e74c3c;
    --border-radius: 12px;
    
    --config-panel-bg: #f8fafc;
    --config-panel-border: #e2e8f0;
    --toggle-container-bg: #e2e8f0;
    --toggle-label-color: #475569;
    --input-border: #cbd5e1;
    --nav-btn-bg: #e2e8f0;
    --nav-btn-text: #475569;
    --nav-btn-hover: #cbd5e1;
    --grid-bg: #f8fafc;
    --table-header-bg: #f8f9fa;
}

.grid-layout { 
    display: grid; 
    grid-template-columns: repeat(6, 1fr); 
    gap: 6px; 
    max-height: 230px; /* Bumped from 180px for better density */
    overflow-y: auto; 
    padding: 5px; 
    background: var(--grid-bg); 
    border: 1px solid var(--config-panel-border); 
    border-radius: 8px; 
    margin-bottom: 15px; 
}

/* Dark Palette Overrides */
[data-theme="dark"] {
    --bg-color: #121824;
    --card-bg: #1e293b;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --primary: #38bdf8;
    --success: #4ade80;
    --error: #f87171;
    
    --config-panel-bg: #0f172a;
    --config-panel-border: #334155;
    --toggle-container-bg: #334155;
    --toggle-label-color: #cbd5e1;
    --input-border: #475569;
    --nav-btn-bg: #334155;
    --nav-btn-text: #cbd5e1;
    --nav-btn-hover: #475569;
    --grid-bg: #0f172a;
    --table-header-bg: #0f172a;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 15px;
    transition: background-color 0.25s ease, color 0.25s ease;
}

.hidden { display: none !important; }

#sign-video-player {
    width: 100%;       /* Match your sign-viewer styling */
    max-width: 400px;  /* Example boundary */
    border-radius: 8px;
    background: #000;  /* Clean backing color while loading */
}

/* Mirror support for your left-handed toggle preference */
#sign-video-player.left-handed-mirror {
    transform: scaleX(-1);
}

/* Handedness Dynamic Real-Time Mirror Engine Modifier */
.left-handed-mirror {
    transform: scaleX(-1) !important;
}

/* Portrait Safety Navigation Layout */
.navigation-row {
    width: 100%;
    display: flex;
    justify-content: flex-start;
    margin-bottom: 15px;
}
.btn-back {
    background: var(--nav-btn-bg);
    color: var(--nav-btn-text);
    padding: 8px 14px;
    font-size: 0.85rem;
    border-radius: 6px;
    border: none;
    cursor: pointer;
    font-weight: 600;
}
.btn-back:hover {
    background: var(--nav-btn-hover);
}

/* Configuration UI Settings Panel Block Layouts */
.config-panel {
    background: var(--config-panel-bg);
    border: 1px solid var(--config-panel-border);
    border-radius: 8px;
    padding: 15px;
    margin-bottom: 20px;
}
.config-row {
    display: flex;
    justify-content: space-between;
    align-items: center; /* Clean vertical baseline centering alignment */
    width: 100%;
}
.config-label {
    font-size: 0.85rem;
    font-weight: bold;
    color: var(--text-muted);
    text-transform: uppercase;
}

/* Theme toggle interaction element */
.btn-theme {
    background: var(--nav-btn-bg);
    color: var(--text-main);
    padding: 6px 12px;
    font-size: 0.85rem;
    font-weight: 600;
    border-radius: 6px;
    border: none;
}

.hand-toggle-container {
    display: flex;
    background: var(--toggle-container-bg);
    padding: 3px;
    border-radius: 6px;
    min-width: 200px;
}
.hand-toggle-container input[type="radio"] {
    display: none;
}
.hand-label {
    flex: 1;
    text-align: center;
    padding: 8px;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--toggle-label-color);
    cursor: pointer;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.15s ease;
}
.hand-toggle-container input[type="radio"]:checked + .hand-label {
    background: var(--card-bg);
    color: var(--text-main);
    box-shadow: 0 2px 4px rgba(0,0,0,0.15);
}

/* Unified Layout Sizing Parameters across components */
.app-container {
    width: 100%;
    max-width: 500px;
    background: var(--card-bg);
    padding: 25px;
    border-radius: var(--border-radius);
    box-shadow: 0 10px 25px rgba(0,0,0,0.08);
    transition: background-color 0.25s ease;
}

header { 
    text-align: center; 
    margin-bottom: 25px; 
}
header h1 { 
    font-size: 1.6rem; 
    color: var(--text-main); 
    margin-bottom: 5px; 
}
header p { 
    font-size: 0.9rem; 
    color: var(--text-muted); 
}

/* Action button variations */
.hub-actions { display: flex; flex-direction: column; gap: 12px; }
.btn-primary-large { background: var(--primary); color: #fff; padding: 18px; border-radius: 10px; font-size: 1.1rem; font-weight: bold; border: none; cursor: pointer; }
.btn-success-large { background: var(--success); color: #fff; padding: 18px; border-radius: 10px; font-size: 1.1rem; font-weight: bold; border: none; cursor: pointer; }

/* Mode Selection Tab Bars */
.mode-tabs { display: flex; gap: 5px; margin-bottom: 20px; background: var(--config-panel-bg); padding: 4px; border-radius: 8px; }
.tab-btn { flex: 1; border: none; padding: 8px; font-size: 0.85rem; font-weight: bold; background: none; border-radius: 6px; cursor: pointer; color: var(--text-muted); }
.tab-btn.active { background: var(--card-bg); color: var(--text-main); box-shadow: 0 2px 5px rgba(0,0,0,0.1); }

/* Revision Study Matrix Layouts */
.help-text { font-size: 0.8rem; color: var(--text-muted); text-align: center; margin-bottom: 10px; }
.grid-layout { display: grid; grid-template-columns: repeat(6, 1fr); gap: 6px; max-height: 180px; overflow-y: auto; padding: 5px; background: var(--grid-bg); border: 1px solid var(--config-panel-border); border-radius: 8px; margin-bottom: 15px; }
.grid-cell { padding: 8px 4px; border: 1px solid var(--input-border); background: var(--card-bg); color: var(--text-main); border-radius: 6px; font-weight: bold; font-size: 0.9rem; text-align: center; cursor: pointer; }
.grid-cell:hover { background: var(--config-panel-bg); border-color: var(--primary); }

.revision-viewer-card { background: var(--config-panel-bg); border: 2px dashed var(--config-panel-border); border-radius: 8px; padding: 15px; text-align: center; }
.viewer-label { font-weight: bold; font-size: 1.1rem; margin-top: 10px; text-transform: uppercase; color: var(--primary); }

/* Quick Recognition Flash Test Layouts */
.options-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.btn-option { padding: 12px 5px; background: var(--card-bg); color: var(--text-main); border: 2px solid var(--input-border); border-radius: 8px; font-weight: bold; font-size: 1rem; cursor: pointer; text-transform: uppercase; }
.btn-option:hover { border-color: var(--primary); background: var(--config-panel-bg); }

/* Primary Core Application Components */
.display-card { background: var(--config-panel-bg); border: 2px solid var(--config-panel-border); border-radius: var(--border-radius); padding: 20px; text-align: center; margin-bottom: 20px; position: relative; }
.image-wrapper { height: 220px; display: flex; justify-content: center; align-items: center; background: transparent; overflow: hidden; }

/* Soft Blending Image Dissolve Transition Rules */
.image-wrapper img { 
    max-height: 100%; 
    max-width: 100%; 
    object-fit: contain; 
    opacity: 1;
    transition: opacity 0.08s ease-in-out, transform 0.1s ease; 
}
.image-wrapper img.fade-out {
    opacity: 0;
}

.controls-panel { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-bottom: 20px; }
.control-group { grid-column: span 1; display: flex; flex-direction: column; font-size: 0.85rem; font-weight: 600; color: var(--text-main); }
.control-group label { margin-bottom: 4px; }
.control-group select, .control-group input { padding: 8px; border-radius: 6px; border: 1px solid var(--input-border); background: var(--card-bg); color: var(--text-main); }

button { padding: 12px; border: none; border-radius: 8px; font-weight: bold; cursor: pointer; transition: background 0.2s; }
button:disabled { opacity: 0.4; cursor: not-allowed; }
.btn-primary { background: var(--primary); color: #fff; grid-column: span 1; }
.btn-secondary { background: #95a5a6; color: #fff; grid-column: span 1; }

/* Vertical Stacked Panel For Portrait Aspect Layout Optimization */
.stacked-input-panel {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 20px;
}
.stacked-input-panel input {
    width: 100%;
    padding: 14px;
    border: 2px solid var(--input-border);
    background: var(--card-bg);
    color: var(--text-main);
    border-radius: 8px;
    font-size: 1.1rem;
    text-align: center;
}
.stacked-input-panel button {
    width: 100%;
    padding: 14px;
    font-size: 1rem;
}

#user-guess { text-transform: uppercase; }
#user-guess:focus, #username-input:focus { border-color: var(--primary); outline: none; }
.btn-success { background: var(--success); color: #fff; }

#status-indicator { margin-top: 10px; font-size: 0.85rem; font-weight: bold; text-transform: uppercase; letter-spacing: 1px; }
.status-idle { color: var(--text-muted); }
.status-playing { color: var(--primary); }

.feedback-container { text-align: center; font-weight: bold; min-height: 24px; padding: 8px; border-radius: 6px; }
.correct { background: rgba(46, 204, 113, 0.15); color: var(--success); }
.incorrect { background: rgba(231, 76, 60, 0.15); color: var(--error); }

.divider { border: 0; height: 1px; background: var(--config-panel-border); margin: 25px 0; }
.dashboard-panel h3 { font-size: 1rem; margin-bottom: 12px; color: var(--text-main); text-transform: uppercase; letter-spacing: 0.5px; }

/* Metrics Dash & Table Structures */
.metrics-table { width: 100%; border-collapse: collapse; font-size: 0.85rem; margin-bottom: 15px; text-align: left; }
.metrics-table th, .metrics-table td { padding: 10px; border-bottom: 1px solid var(--config-panel-border); color: var(--text-main); }
.metrics-table th { background: var(--table-header-bg); color: var(--text-muted); font-weight: 600; }
.btn-review-mistakes { background: var(--nav-btn-bg); color: var(--nav-btn-text); padding: 4px 8px; font-size: 0.75rem; border-radius: 4px; font-weight: bold; }
.btn-review-mistakes:hover { background: var(--nav-btn-hover); }

.csv-actions { display: flex; gap: 10px; }
.btn-dash { flex: 1; background: #7f8c8d; color: white; font-size: 0.8rem; padding: 8px; border-radius: 6px; }
.btn-dash-label { flex: 1; background: #2c3e50; color: white; font-size: 0.8rem; padding: 8px; border-radius: 6px; font-weight: bold; text-align: center; cursor: pointer; display: flex; align-items: center; justify-content: center; }

/* Modal Overlay Structural Mechanics */
.modal-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.5); display: flex; justify-content: center; align-items: center; z-index: 1000; }
.modal-content { background: var(--card-bg); padding: 25px; border-radius: var(--border-radius); width: 90%; max-width: 400px; box-shadow: 0 15px 30px rgba(0,0,0,0.3); border: 1px solid var(--config-panel-border); }
.modal-header { display: flex; justify-content: space-between; align-items: center; border-bottom: 1px solid var(--config-panel-border); padding-bottom: 10px; margin-bottom: 15px; }
.modal-header h2 { font-size: 1.2rem; color: var(--text-main); }
.btn-close { background: none; border: none; font-size: 1.5rem; color: var(--text-muted); cursor: pointer; line-height: 1; padding: 0 5px; }
.modal-body { max-height: 250px; overflow-y: auto; font-size: 0.9rem; }
.mistake-row { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px dashed var(--config-panel-border); }
.mistake-count { background: rgba(231, 76, 60, 0.15); color: var(--error); font-weight: bold; padding: 2px 8px; border-radius: 12px; font-size: 0.8rem; }
.no-mistakes-msg { color: var(--text-muted); text-align: center; padding: 20px 0; font-style: italic; }
/* Trainer Mask Overlay */
.image-wrapper {
    position: relative;
}

#trainer-mask-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 15%;
    z-index: 10;
    pointer-events: none;
    box-sizing: border-box;
}

#trainer-mask-overlay.trainer-mask-hidden {
    display: none;
}

/* Media Frame — wraps media so mask overlay is relative to actual media, not container */
.media-frame {
    position: relative;
    display: inline-block;
    line-height: 0;
    max-width: 100%;
    max-height: 100%;
}

.media-frame img,
.media-frame video {
    display: block;
    max-width: 100%;
    max-height: 220px;
    width: auto;
    height: auto;
    border-radius: 8px;
}