body {
    font-family: 'Noto Sans KR', 'Roboto', sans-serif;
    background-color: #f4f7f6;
    color: #333;
    line-height: 1.7;
    margin: 0;
}

.app-container {
    max-width: 900px;
    margin: 30px auto;
    padding: 20px;
}

/* Header */
.app-header {
    text-align: center;
    margin-bottom: 40px;
}

.app-header h1 {
    font-size: 2.8rem;
    color: #005a9c; /* Deep Blue */
    margin: 0;
}

.app-header p {
    font-size: 1.2rem;
    color: #5a7d9c;
}

/* Converter & Content Cards */
.converter-tool > *, .content-guide {
    background-color: #ffffff;
    border-radius: 12px;
    padding: 30px;
    margin-bottom: 25px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.07);
}

/* Tabs */
.tabs {
    display: flex;
    border-bottom: 2px solid #e9eff3;
    margin-bottom: 25px;
}

.tab-btn {
    padding: 15px 25px;
    font-size: 1.1rem;
    font-weight: bold;
    background-color: transparent;
    border: none;
    border-bottom: 3px solid transparent;
    cursor: pointer;
    color: #5a7d9c;
    transition: all 0.2s ease-in-out;
    margin-bottom: -2px; /* Align with parent border */
}

.tab-btn.active {
    color: #005a9c;
    border-bottom-color: #005a9c;
}

.tab-btn:hover {
    background-color: #f4f7f6;
}

/* Converter Section */
.converter-section {
    display: none;
}

.converter-section.active {
    display: block;
}

.input-row {
    display: flex;
    align-items: flex-end;
    gap: 20px;
    flex-wrap: wrap;
}

.input-group {
    flex: 1;
    min-width: 150px;
}

.input-group label {
    display: block;
    font-weight: bold;
    margin-bottom: 8px;
    color: #333;
}

.input-group input[type="number"], .input-group select {
    width: 100%;
    padding: 12px;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 1rem;
    background-color: #fdfdfd;
}

.equals-sign {
    font-size: 2rem;
    font-weight: bold;
    color: #005a9c;
    padding-bottom: 10px;
}

.result-area {
    margin-top: 30px;
    padding: 20px;
    background-color: #e9f5ff;
    border-radius: 8px;
    text-align: center;
}

.result-area p {
    margin: 0;
    font-size: 1.5rem;
    font-weight: bold;
    color: #005a9c;
}

/* Content Guide Section */
.content-guide h2, .content-guide h3, .content-guide h4 {
    color: #005a9c;
    border-bottom: 2px solid #e9eff3;
    padding-bottom: 10px;
    margin-top: 25px;
}

.content-guide p,
.content-guide li {
    color: #444;
    font-size: 1.05rem;
}

.content-guide ol,
.content-guide ul {
    padding-left: 20px;
    margin-top: 10px;
}

.content-guide .disclaimer {
    margin-top: 30px;
    padding: 15px;
    background-color: #fffbe6;
    border-left: 5px solid #f0ad4e; /* Warning yellow */
    font-style: italic;
}

/* Footer */
.app-footer {
    text-align: center;
    margin-top: 50px;
    color: #777;
}

.app-footer a {
    color: #005a9c;
    text-decoration: none;
}

.app-footer a:hover {
    text-decoration: underline;
}