:root {
            --primary-color: #c62828; /* قرمز برای گرما */
            --secondary-color: #ef5350;
            --bg-color: #f4f7f6;
            --sidebar-bg: #b71c1c;
            --text-color: #333;
            --white: #ffffff;
            --border-radius: 8px;
            --shadow: 0 4px 6px rgba(0,0,0,0.1);
        }
        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: "vazirmatn", 'Tahoma', 'Segoe UI', Geneva, Verdana, sans-serif;
            
            /* Scrollbar Styles */
            scrollbar-width: thin;
            scrollbar-color: var(--secondary-color) #f0f0f0;
        }
        /* Custom Scrollbar for Webkit */
        ::-webkit-scrollbar {
            width: 8px;
            height: 8px;
        }
        ::-webkit-scrollbar-track {
            background: #f1f1f1;
            border-radius: 4px;
        }
        ::-webkit-scrollbar-thumb {
            background: var(--secondary-color);
            border-radius: 4px;
        }
        ::-webkit-scrollbar-thumb:hover {
            background: var(--primary-color);
        }
        html {
            scroll-behavior: smooth;
        }
        body {
            background-color: var(--bg-color);
            color: var(--text-color);
            display: flex;
            flex-direction: column;
            height: 100vh;
            overflow: hidden;
        }
        /* Language Switcher Header */
        .top-bar {
            background-color: var(--white);
            padding: 10px 20px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            box-shadow: 0 2px 4px rgba(0,0,0,0.05);
            z-index: 100;
            flex-shrink: 0;
        }
        .lang-btn {
            background-color: var(--primary-color);
            color: white;
            border: none;
            padding: 6px 12px;
            border-radius: 4px;
            cursor: pointer;
            font-size: 0.9rem;
            transition: background 0.3s;
        }
        .lang-btn:hover {
            background-color: var(--secondary-color);
        }
        /* Layout Container */
        .layout-wrapper {
            display: flex;
            flex: 1;
            overflow: hidden;
        }
        /* Sidebar Styles */
        .sidebar {
            width: 280px;
            background-color: var(--sidebar-bg);
            color: var(--white);
            display: flex;
            flex-direction: column;
            padding: 20px;
            box-shadow: 2px 0 5px rgba(0,0,0,0.1);
            transition: all 0.3s ease;
            flex-shrink: 0;
            overflow-y: auto;
        }
        .sidebar h2 {
            font-size: 1.2rem;
            margin-bottom: 30px;
            text-align: center;
            border-bottom: 1px solid rgba(255,255,255,0.2);
            padding-bottom: 15px;
        }
        .nav-btn {
            background: none;
            border: none;
            color: rgba(255,255,255,0.8);
            padding: 12px 15px;
            text-align: inherit;
            cursor: pointer;
            font-size: 0.95rem;
            border-radius: var(--border-radius);
            margin-bottom: 8px;
            transition: background 0.2s, color 0.2s;
        }
        .nav-btn:hover {
            background-color: rgba(255,255,255,0.1);
            color: var(--white);
        }
        .nav-btn.active {
            background-color: var(--secondary-color);
            color: var(--white);
            font-weight: bold;
        }
        /* Main Content Styles */
        .main-content {
            flex: 1;
            padding: 40px;
            overflow-y: auto;
            position: relative;
        }
        .tool-container {
            display: none;
            background: var(--white);
            padding: 30px;
            border-radius: var(--border-radius);
            box-shadow: var(--shadow);
            max-width: 850px;
            margin: 0 auto;
            animation: fadeIn 0.4s ease-in-out;
        }
        .tool-container.active {
            display: block;
        }
        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        .tool-header {
            margin-bottom: 25px;
            border-bottom: 2px solid var(--bg-color);
            padding-bottom: 15px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 10px;
        }
        .tool-header h1 {
            color: var(--primary-color);
            font-size: 1.5rem;
        }
        .tool-header p {
            color: #666;
            font-size: 0.9rem;
            margin-top: 5px;
        }
        /* Form Elements */
        .form-group {
            margin-bottom: 20px;
        }
        .form-group label {
            display: block;
            margin-bottom: 8px;
            font-weight: bold;
            font-size: 0.9rem;
        }
        .form-group input {
            width: 100%;
            padding: 10px;
            border: 1px solid #ddd;
            border-radius: var(--border-radius);
            font-size: 1rem;
            transition: border-color 0.3s;
        }
        .form-group input:focus {
            border-color: var(--secondary-color);
            outline: none;
        }
        .calc-btn {
            background-color: var(--primary-color);
            color: var(--white);
            border: none;
            padding: 12px 25px;
            font-size: 1rem;
            border-radius: var(--border-radius);
            cursor: pointer;
            width: 100%;
            transition: background 0.3s;
            margin-top: 10px;
        }
        .calc-btn:hover {
            background-color: var(--secondary-color);
        }
        .print-btn {
            background-color: #555;
            color: white;
            border: none;
            padding: 8px 15px;
            border-radius: 4px;
            cursor: pointer;
            font-size: 0.85rem;
        }
        .print-btn:hover { background-color: #333; }
        
        /* Result Box */
        .result-box {
            margin-top: 30px;
            padding: 20px;
            background-color: #ffebee;
            border: 1px solid #ffcdd2;
            border-radius: var(--border-radius);
            display: none;
        }
        .result-box h3 {
            color: var(--primary-color);
            margin-bottom: 10px;
            font-size: 1.1rem;
        }
        .result-value {
            font-size: 1.2rem;
            font-weight: bold;
            color: #c62828;
        }
        /* Steps Box Styles (New) */
        .steps-box {
            margin-top: 20px;
            padding: 20px;
            background-color: #fff3e0; /* نارنجی روشن برای تم گرما */
            border: 1px solid #ffe0b2;
            border-radius: var(--border-radius);
            display: none;
        }
        .steps-box h4 {
            color: #e65100;
            margin-bottom: 15px;
            font-size: 1rem;
            border-bottom: 1px solid #ffe0b2;
            padding-bottom: 8px;
        }
        .step-item {
            margin-bottom: 12px;
            font-size: 0.95rem;
            line-height: 1.6;
        }
        .step-item strong {
            color: #bf360c;
        }
        .formula {
            font-family: 'Courier New', Courier, monospace;
            background: rgba(255,255,255,0.6);
            padding: 2px 6px;
            border-radius: 4px;
            direction: ltr; /* فرمول‌ها همیشه چپ به راست */
            display: inline-block;
        }
        /* Responsive Design */
        @media (max-width: 768px) {
            .layout-wrapper {
                flex-direction: column;
            }
            .sidebar {
                width: 100%;
                flex-direction: row;
                overflow-x: auto;
                padding: 10px;
                align-items: center;
                height: auto;
                flex-shrink: 0;
                white-space: nowrap;
                -ms-overflow-style: none;
                scrollbar-width: none;
            }
            .sidebar::-webkit-scrollbar {
                display: none;
            }
            .sidebar h2 {
                display: none;
            }
            .nav-btn {
                margin-bottom: 0;
                margin-left: 10px;
                margin-right: 0;
                font-size: 0.85rem;
                padding: 8px 12px;
                flex-shrink: 0;
            }
            html[dir="ltr"] .nav-btn {
                margin-left: 0;
                margin-right: 10px;
            }
            .main-content {
                padding: 20px;
            }
            .tool-header {
                flex-direction: column;
                align-items: flex-start;
            }
            .print-btn {
                width: 100%;
                margin-top: 10px;
            }
        }
        /* Print Styles */
        @media print {
            .top-bar, .sidebar, .calc-btn, .print-btn {
                display: none !important;
            }
            body {
                background-color: white;
                height: auto;
                overflow: visible;
                display: block;
            }
            .layout-wrapper {
                display: block;
            }
            .main-content {
                padding: 0;
                overflow: visible;
            }
            .tool-container {
                box-shadow: none;
                border: 1px solid #ddd;
                max-width: 100%;
                display: block !important;
            }
            .tool-container:not(.active) {
                display: none !important;
            }
            .steps-box, .result-box {
                display: block !important;
                border: 1px solid #ccc;
                background: none;
            }
        }