:root[data-theme="light"] {
    --bg: #ffffff;
    --sidebar-bg: #f3f4f6;
    --text: #1f2937;
    --border: #d1d5db;
    --accent: #3b82f6;
    --tab-active: #ffffff;
    --tab-inactive: #e5e7eb;
}

:root[data-theme="dark"] {
    --bg: #111827;
    --sidebar-bg: #1f2937;
    --text: #f9fafb;
    --border: #374151;
    --accent: #60a5fa;
    --tab-active: #111827;
    --tab-inactive: #1f2937;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: background-color 0.3s, color 0.3s;
}

/* Navbar */
nav {
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 20px;
    background-color: var(--sidebar-bg);
    border-bottom: 1px solid var(--border);
    transition: background-color 0.3s, border-color 0.3s;
    flex-shrink: 0;
}

.logo { font-weight: bold; font-size: 1.2rem; display: flex; align-items: center; gap: 8px; }
.controls { display: flex; gap: 8px; align-items: center; }

select.secondary, button.secondary {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text);
    padding: 6px 10px;
    border-radius: 6px;
    cursor: pointer;
    outline: none;
    font-size: 0.9rem;
}

select.secondary option { background: var(--bg); color: var(--text); }

button {
    background: var(--accent);
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 6px;
}
button:hover { opacity: 0.9; }

/* Main Workspace */
main {
    flex: 1;
    display: flex;
    height: calc(100vh - 60px);
    overflow: hidden;
}

/* Panes & Resizer */
#left-pane {
    width: 50%;
    display: flex;
    flex-direction: column;
    min-width: 200px;
}

#resizer {
    width: 6px;
    background-color: var(--sidebar-bg);
    border-left: 1px solid var(--border);
    border-right: 1px solid var(--border);
    cursor: col-resize;
    z-index: 10;
    transition: background-color 0.2s;
}
#resizer:hover, #resizer:active { background-color: var(--accent); }

#right-pane {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-width: 200px;
}

.pane-header {
    padding: 0;
    background: var(--sidebar-bg);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
}

/* Tabs System */
.tabs-container {
    display: flex;
    flex: 1;
    overflow-x: auto;
    scrollbar-width: none; 
}
.tabs-container::-webkit-scrollbar { display: none; }

.tab {
    padding: 8px 14px;
    font-size: 0.85rem;
    background: var(--tab-inactive);
    border-right: 1px solid var(--border);
    display: flex;
    align-items: center;
    gap: 12px;
    color: var(--text);
    opacity: 0.7;
    user-select: none;
}
.tab.active {
    background: var(--bg);
    opacity: 1;
    border-bottom: 2px solid var(--accent);
}

.tab-name {
    display: flex;
    align-items: center;
    gap: 6px;
    cursor: pointer;
}

.tab-close {
    cursor: pointer;
    opacity: 0.5;
    transition: opacity 0.2s, color 0.2s;
    display: flex;
    align-items: center;
}
.tab-close:hover {
    opacity: 1;
    color: #ef4444; /* Red color on hover */
}

.add-tab-btn {
    background: transparent;
    color: var(--text);
    border: none;
    padding: 10px 15px;
    cursor: pointer;
    opacity: 0.7;
    border-radius: 0;
}
.add-tab-btn:hover { opacity: 1; background: var(--border); }

.right-header-title {
    padding: 10px 16px;
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: bold;
}

/* Editor & Output Containers */
#editor-container {
    flex: 1;
    width: 100%;
    height: 100%;
    overflow: hidden;
    background: var(--bg);
}

#output-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    background-color: var(--bg);
}

iframe {
    flex: 1;
    width: 100%;
    height: 100%;
    border: none;
    background: transparent;
}

#loading {
    padding: 20px;
    font-family: monospace;
    color: var(--text);
}