body {
                background: #f7fbff;
                margin: 0;
                font-family: "Segoe UI", Arial, sans-serif;
                color: #245;
            }
            .container {
                max-width: 430px;
                margin: 38px auto 0 auto;
                background: #fff;
                border-radius: 17px;
                box-shadow: 0 4px 24px #236de420;
                padding: 28px 14px 20px 14px;
            }
            .logo {
                font-size: 1.4em;
                font-weight: bold;
                color: #236de4;
                text-align: center;
                margin-bottom: 11px;
                letter-spacing: -1px;
            }
            .desc {
                color: #286673;
                text-align: center;
                margin-bottom: 17px;
                font-size: 0.74em;
            }
            .mode-toggle {
                display: flex;
                gap: 8px;
                margin: 12px 0 19px 0;
                justify-content: center;
                flex-wrap: wrap;
            }
            .toggle-btn {
                flex: 1 1 70px;
                background: #f4f8fe;
                color: #236de4;
                border: 1.3px solid #d1e2fc;
                border-radius: 8px;
                font-size: 1em;
                font-weight: 600;
                padding: 0.63em 0;
                cursor: pointer;
                transition:
                    background 0.15s,
                    color 0.13s;
                outline: none;
                margin-bottom: 2px;
            }
            .toggle-btn.active {
                background: #236de4;
                color: #fff;
                border-color: #236de4;
                box-shadow: 0 3px 14px #236de420;
            }
            .row {
                display: flex;
                align-items: center;
                gap: 10px;
                margin: 13px 0;
            }
            .row label {
                min-width: 90px;
                color: #376;
                font-size: 1em;
            }
            .row input,
            .row select {
                flex: 1;
                padding: 8px 9px;
                font-size: 1.09em;
                border: 1.2px solid #badcff;
                border-radius: 7px;
                background: #fafdff;
                color: #234;
                margin-left: 0;
                margin-right: 0;
            }
            .result-area {
                text-align: center;
                font-size: 1.18em;
                color: #1d97d6;
                margin: 22px 0 7px 0;
                font-weight: bold;
                min-height: 34px;
            }
            .footer {
                color: #789;
                text-align: center;
                font-size: 0.95em;
                margin-top: 24px;
                line-height: 1.5;
                opacity: 0.88;
            }
            #backBtn {
                position: fixed;
                left: 50%;
                bottom: 32px;
                transform: translateX(-50%);
                background: #236de4;
                color: #fff;
                font-weight: 700;
                border: none;
                border-radius: 2rem;
                padding: 0.58em 1.5em;
                box-shadow: 0 4px 16px #236de433;
                font-size: 1.09em;
                text-decoration: none;
                cursor: pointer;
                letter-spacing: 0.01em;
                transition:
                    background 0.15s,
                    transform 0.12s;
                z-index: 2000;
            }
            #backBtn:hover {
                background: #143e77;
                transform: translateX(-50%) scale(1.04);
            }
            @media (max-width: 600px) {
                .container {
                    max-width: 99vw;
                    padding: 9px 2vw 12px 2vw;
                }
                #backBtn {
                    bottom: 18px;
                    font-size: 0.98em;
                    padding: 0.48em 1em;
                }
            }