:root {
    --primary-bg: #1e293b;
    --panel-bg: #ffffff;
    --accent: #3b82f6;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --success: #10b981;
    --error: #ef4444;
    --warning: #f59e0b;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: 'Inter', sans-serif; background-color: #f8fafc; display: flex; min-height: 100vh; color: var(--text-main); }

/* --- SIDEBAR --- */
.sidebar {
    width: 380px;
    background-color: var(--primary-bg);
    color: #e2e8f0;
    display: flex;
    flex-direction: column;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
    border-right: 1px solid #334155;
    z-index: 100;
}

.back-btn {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 1.5rem;
    color: #94a3b8;
    text-decoration: none;
    transition: all 0.2s;
    border-bottom: 1px solid #334155;
    font-weight: 600;
}

.back-btn:hover {
    color: white;
    background: #334155;
}

.input-panel {
    padding: 1.5rem;
}

/* --- MAIN CONTENT --- */
.content-area, .main-content, .results-panel, .main-area, .main-view, .output-area {
    margin-left: 380px;
    flex: 1;
    padding: 2rem;
    display: flex;
    flex-direction: column;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    color: white;
    padding: 2.5rem;
    border-radius: 16px;
    margin-bottom: 2rem;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1);
}

.hero h1 { font-size: 2rem; margin-bottom: 0.5rem; }
.hero p { font-size: 1rem; color: #94a3b8; }

.panel-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: #fff;
    border-bottom: 1px solid #334155;
    padding-bottom: 0.5rem;
}

.form-group { margin-bottom: 1rem; }
.form-row { display: flex; gap: 10px; }
.form-col { flex: 1; }

input, select {
    width: 100%;
    padding: 0.6rem;
    background-color: #334155;
    border: 1px solid #475569;
    border-radius: 6px;
    color: #fff;
    font-size: 0.9rem;
}

label {
    display: block;
    font-size: 0.85rem;
    color: #cbd5e1;
    margin-bottom: 0.25rem;
}

.section-header {
    font-size: 0.9rem;
    font-weight: 700;
    color: #fff;
    margin: 1.5rem 0 0.75rem 0;
    padding-bottom: 0.25rem;
    border-bottom: 1px solid #334155;
}

input:focus, select:focus {
    outline: none;
    border-color: var(--accent);
}

.calc-btn, .btn-calc, .action-btn {
    background-color: var(--accent);
    color: white;
    border: none;
    padding: 0.8rem;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    margin-top: 1rem;
    transition: background 0.2s;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
}
.calc-btn:hover, .btn-calc:hover, .action-btn:hover { background-color: #2563eb; }

.card {
    background: var(--panel-bg);
    border-radius: 12px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    padding: 1.5rem;
    border: 1px solid var(--border-color);
}

.result-row {
    display: flex;
    justify-content: space-between;
    border-bottom: 1px solid #f1f5f9;
    padding: 0.5rem 0;
}
.result-row:last-child { border-bottom: none; }
.result-label { color: var(--text-muted); }
.result-value { font-weight: 600; color: var(--text-main); }

@media (max-width: 900px) {
    .sidebar { display: none; }
    .content-area, .main-content, .results-panel, .main-area, .main-view, .output-area { margin-left: 0; }
}