/* --- 기본 & 폰트 설정 --- */
body {
    font-family: 'Helvetica Neue', Arial, sans-serif;
    background-color: #f4f7f9;
    color: #333;
    margin: 0;
    line-height: 1.6;
}

/* --- 로딩 오버레이 --- */
#loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(255, 255, 255, 0.9);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.spinner {
    border: 6px solid #f3f3f3;
    border-top: 6px solid #3498db;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
    margin-bottom: 20px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* --- 헤더 --- */
header {
    background-color: #ffffff;
    padding: 20px 40px;
    border-bottom: 1px solid #e0e0e0;
    text-align: center;
}

header h1 {
    margin: 0;
    color: #2c3e50;
    font-size: 2em;
}

/* --- 정보 섹션 --- */
.info-section {
    background-color: #e9f7ef;
    padding: 20px;
    margin: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
    line-height: 1.8;
}

.info-section h2 {
    color: #28a745;
    text-align: center;
    margin-bottom: 20px;
}

.info-section h3 {
    color: #3498db;
    margin-top: 25px;
    margin-bottom: 10px;
}

.info-section ul, .info-section ol {
    list-style-position: inside;
    padding-left: 20px;
}
.info-section ul li, .info-section ol li {
    margin-bottom: 8px;
}

.info-section p {
    text-align: justify;
    margin-bottom: 15px;
}


/* --- 메인 컨테이너 --- */
.main-container {
    display: flex;
    padding: 20px;
    gap: 20px;
}

/* --- 좌측 컨트롤 패널 --- */
.control-panel {
    flex: 1;
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
    min-width: 300px;
}

.control-panel h2 {
    margin-top: 0;
    border-bottom: 2px solid #3498db;
    padding-bottom: 10px;
    color: #2c3e50;
}

.control-group {
    margin-bottom: 20px;
}

.control-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: bold;
    color: #555;
}

input[type="text"] {
    width: 100%;
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 4px;
    box-sizing: border-box;
    font-size: 0.95em;
}

/* --- XY 입력 그리드 스타일 --- */
.grid-label-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
}
.grid-label-container label {
    margin-bottom: 0;
}

#xy-grid {
    width: 100%;
    border-collapse: collapse;
}
#xy-grid th {
    background-color: #e9ecef;
    padding: 6px;
    font-size: 0.9em;
    text-align: center;
}
#xy-grid td {
    padding: 2px;
    vertical-align: middle;
}
#xy-grid input {
    text-align: center;
    padding: 6px;
    font-size: 0.9em;
    border-width: 1px;
    width: 100%;
    box-sizing: border-box;
}
#xy-grid th:last-child, #xy-grid td:last-child {
    width: 30px;
}

.grid-button {
    border: none;
    background-color: #3498db;
    color: white;
    border-radius: 50%;
    cursor: pointer;
    width: 24px;
    height: 24px;
    font-weight: bold;
    line-height: 22px;
    text-align: center;
}
.grid-button.remove-row-button {
    background-color: #e74c3c;
}
.grid-button:hover {
    opacity: 0.8;
}

input[type="range"] {
    width: 100%;
}

/* --- 버튼 그룹 --- */
.button-group {
    display: flex;
    flex-direction: column; /* 버튼을 수직으로 배열 */
    gap: 10px;
}
#run-button {
    width: 100%; /* 너비 전체 사용 */
    padding: 12px;
    background-color: #3498db; /* 이전처럼 파란색 */
    color: white;
    border: none;
    border-radius: 4px;
    font-size: 1.1em;
    cursor: pointer;
    transition: background-color 0.3s;
}

#run-button:hover:not(:disabled) {
    background-color: #2980b9;
}

.copy-equation-button {
    width: 100%; /* 너비 전체 사용 */
    padding: 12px;
    background-color: #2ecc71; /* 초록색 */
    color: white;
    border: none;
    border-radius: 4px;
    font-size: 1.1em;
    cursor: pointer;
    transition: background-color 0.3s;
}

.copy-equation-button:hover:not(:disabled) {
    background-color: #27ae60;
}

button:disabled {
    background-color: #a4cde8;
    cursor: not-allowed;
}


/* --- 우측 그래프 패널 --- */
.graph-panel {
    flex: 2.5;
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
    display: flex;
    flex-direction: column;
}

.graph-panel h2 {
    margin-top: 0;
    border-bottom: 2px solid #2ecc71;
    padding-bottom: 10px;
    color: #2c3e50;
}

#graph-container {
    flex-grow: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 400px;
}

#graph-container img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

.error {
    color: #e74c3c;
    font-weight: bold;
}

/* --- 푸터 --- */
footer {
    background-color: #34495e;
    color: #ecf0f1;
    text-align: center;
    padding: 20px;
    margin-top: 20px;
    font-size: 0.9em;
}

footer a {
    color: #ecf0f1;
    text-decoration: none;
}

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

/* --- 반응형 디자인 --- */
@media (max-width: 768px) {
    .main-container {
        flex-direction: column;
    }
    header {
        padding: 15px 20px;
    }
    header h1 {
        font-size: 1.5em;
    }
    .info-section {
        margin: 10px;
        padding: 15px;
    }
}