* {
            box-sizing: border-box;
        }

        body {
            margin: 0;
            padding: 40px 20px;
            font-family: Arial, Helvetica, sans-serif;
            background: #f5f7fa;
            color: #1f2937;
        }

        .container {
            max-width: 900px;
            margin: 0 auto;
        }

        h1 {
            margin-bottom: 30px;
            font-size: 28px;
        }

        .item {
            background: #ffffff;
            border: 1px solid #dfe4ea;
            border-radius: 8px;
            margin-bottom: 12px;
            overflow: hidden;
            box-shadow: 0 2px 5px rgba(0, 0, 0, 0.04);
        }

        .item-header {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: 18px 20px;
            cursor: pointer;
            transition: background 0.2s ease;
        }

        .item-header:hover {
            background: #f8fafc;
        }

        .title {
            font-size: 17px;
            font-weight: 600;
            color: #1e3a5f;
        }

        .toggle {
            width: 30px;
            height: 30px;
            border: 1px solid #1e3a5f;
            border-radius: 50%;
            background: white;
            color: #1e3a5f;
            font-size: 20px;
            line-height: 26px;
            text-align: center;
            cursor: pointer;
            flex-shrink: 0;
            margin-left: 15px;
        }

        .content {
            display: none;
            padding: 0 20px 20px 20px;
            color: #4b5563;
            line-height: 1.65;
            font-size: 15px;
            border-top: 1px solid #eef1f4;
        }

        .item.open .content {
            display: block;
        }

        .item.open .toggle {
            font-size: 18px;
        }

        @media (max-width: 600px) {
            body {
                padding: 20px 12px;
            }

            h1 {
                font-size: 24px;
            }

            .title {
                font-size: 15px;
            }
        }