:root {
    /* YouTube Dark Theme Base Colors */
    --bg-base: #0f0f0f;
    --text-primary: #f1f1f1;
    --text-secondary: #aaaaaa;
    
    /* Modern YouTube Accents */
    --accent-primary: #f1f1f1;
    --accent-primary-text: #0f0f0f;
    --accent-blue: #3ea6ff; /* YouTube link/focus blue */
    
    /* Windows 11 Fluent Variables */
    --fluent-glass: rgba(33, 33, 33, 0.65);
    --fluent-surface: rgba(255, 255, 255, 0.08);
    --fluent-surface-hover: rgba(255, 255, 255, 0.12);
    --fluent-border: rgba(255, 255, 255, 0.12);
    
    /* Status Colors */
    --error: #ff4e45; /* YT Red */
    --success: #2ba640;
    --warning: #fbc02d;

    /* Geometry */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-pill: 36px;
    --transition-fluent: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    background-color: var(--bg-base);
    /* Subtle background blooms to make the Fluent glass effect pop */
    background-image: 
        radial-gradient(circle at 15% 50%, rgba(255, 255, 255, 0.03), transparent 30%),
        radial-gradient(circle at 85% 30%, rgba(62, 166, 255, 0.04), transparent 30%);
    background-attachment: fixed;
    color: var(--text-primary);
    font-family: "Segoe UI Variable Display", "Segoe UI", "Roboto", "Helvetica Neue", sans-serif;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
}

.container {
    width: 100%;
    max-width: 760px;
    padding: 60px 20px;
    box-sizing: border-box;
}

h1 { 
    margin-top: 0; 
    font-weight: 600; 
    font-size: 28px;
    letter-spacing: -0.5px;
}

p { 
    color: var(--text-secondary); 
    font-size: 15px;
}

/* Glassmorphism Panel (Fluent) */
.fluent-panel {
    background: var(--fluent-glass);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border: 1px solid var(--fluent-border);
    border-radius: var(--radius-md);
    padding: 32px;
    box-shadow: 0 16px 40px rgba(0, 0, 0, 0.4);
}

/* Login Screen */
#login-screen { 
    text-align: center; 
    margin-top: 8vh; 
    transition: opacity 0.4s ease, visibility 0.4s; 
}
.login-icon {
    margin-bottom: 16px;
    filter: brightness(0) invert(1); /* Ensure it's white */
}
.divider { 
    margin: 24px 0; 
    color: var(--text-secondary); 
    font-size: 13px;
    display: flex;
    align-items: center;
    text-transform: uppercase;
    letter-spacing: 1px;
}
.divider::before, .divider::after {
    content: '';
    flex: 1;
    border-bottom: 1px solid var(--fluent-border);
    margin: 0 16px;
}

/* App Screen */
#app-screen { 
    opacity: 0; 
    visibility: hidden; 
    transition: opacity 0.4s ease, visibility 0.4s; 
}

/* YouTube Style Tabs */
.tabs { 
    display: flex; 
    gap: 12px; 
    margin-bottom: 24px; 
    overflow-x: auto;
}
.tab { 
    background: var(--fluent-surface); 
    border: 1px solid transparent; 
    color: var(--text-primary); 
    font-size: 15px; 
    font-weight: 500; 
    padding: 10px 20px; 
    border-radius: var(--radius-sm); 
    cursor: pointer; 
    transition: var(--transition-fluent);
    display: flex;
    align-items: center;
}
.tab:hover { 
    background: var(--fluent-surface-hover); 
}
.tab.active { 
    background: var(--accent-primary); 
    color: var(--accent-primary-text); 
}

.tab-content {
    display: none;
    opacity: 0;
    transform: translateY(10px);
    transition: opacity 0.3s ease, transform 0.3s ease;
}
.tab-content.active {
    display: block;
    opacity: 1;
    transform: translateY(0);
}

/* Form Elements (Windows 11 + YouTube Blend) */
.form-group { margin-bottom: 24px; }
label { 
    display: block; 
    margin-bottom: 8px; 
    font-size: 14px; 
    font-weight: 500;
    color: var(--text-primary); 
}
input[type="text"], input[type="number"] {
    width: 100%; 
    padding: 14px 16px; 
    border-radius: var(--radius-sm); 
    border: 1px solid var(--fluent-border);
    border-bottom: 2px solid var(--fluent-border); /* Fluent bottom accent */
    background: rgba(0, 0, 0, 0.2); 
    color: var(--text-primary); 
    box-sizing: border-box; 
    font-size: 16px;
    font-family: inherit;
    transition: var(--transition-fluent);
}
input[type="text"]::placeholder, input[type="number"]::placeholder {
    color: #666666;
}
input[type="text"]:focus, input[type="number"]:focus {
    outline: none; 
    background: rgba(0, 0, 0, 0.4);
    border-color: var(--fluent-border);
    border-bottom-color: var(--accent-blue); /* YouTube/Windows blue focus */
}

/* Buttons (Modern YouTube Pills) */
.btn {
    background: var(--fluent-surface); 
    color: var(--text-primary); 
    border: 1px solid var(--fluent-border);
    padding: 10px 24px; 
    border-radius: var(--radius-pill); 
    cursor: pointer; 
    font-size: 14px; 
    font-weight: 600;
    font-family: inherit;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition-fluent);
}
.btn:hover { 
    background: var(--fluent-surface-hover); 
}
.btn:active {
    transform: scale(0.97);
}

.btn-primary { 
    background: var(--accent-primary); 
    color: var(--accent-primary-text); 
    border: none; 
    padding: 12px 24px;
}
.btn-primary:hover { 
    background: #d9d9d9; 
}
.btn-full { 
    width: 100%; 
    margin-top: 8px; 
    font-size: 15px; 
    padding: 14px 24px;
}

/* File Input */
input[type="file"] { display: none; }
.file-label { margin-right: 15px; }

/* Status */
#status-msg { 
    margin-top: 20px; 
    text-align: center; 
    font-weight: 500; 
    font-size: 14px;
    padding: 12px;
    border-radius: var(--radius-sm);
    transition: var(--transition-fluent); 
}
#status-msg:not(:empty) {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--fluent-border);
}
.text-error { color: var(--error); }
.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-secondary { color: var(--text-secondary); font-size: 14px;}

/* Table (Fluent Rows) */
.table-container { 
    overflow-x: auto; 
    border-radius: var(--radius-sm);
    border: 1px solid var(--fluent-border);
    background: rgba(0, 0, 0, 0.2);
}
table { 
    width: 100%; 
    border-collapse: collapse; 
}
th, td { 
    padding: 16px; 
    text-align: left; 
    border-bottom: 1px solid var(--fluent-border); 
}
th { 
    color: var(--text-secondary); 
    font-weight: 600; 
    font-size: 13px; 
    text-transform: uppercase;
    letter-spacing: 0.5px;
}
tr:last-child td { border-bottom: none; }
tr { transition: var(--transition-fluent); }
tr:hover { background: var(--fluent-surface); }

/* User badge */
.user-badge {
    display: inline-flex;
    align-items: center;
    background: rgba(0,0,0,0.3); 
    padding: 8px 16px;
    border-radius: var(--radius-pill); 
    font-size: 13px; 
    margin-bottom: 24px; 
    border: 1px solid var(--fluent-border);
}
.user-badge strong {
    color: var(--text-primary);
    margin-left: 6px;
}
.logout-link { 
    color: var(--accent-blue); 
    cursor: pointer; 
    margin-left: 16px; 
    font-weight: 600;
    text-decoration: none; 
    transition: var(--transition-fluent);
}
.logout-link:hover {
    text-decoration: underline;
}