:root {
    --bg-color: #f3f4f6;
    --panel-bg: #ffffff;
    --primary-color: #3b82f6;
    --text-color: #1f2937;
    --border-radius: 16px;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
header {
    background-color: var(--panel-bg);
    padding: 1rem 2rem;
    box-shadow: var(--shadow);
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    align-items: center;
    z-index: 10;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

select, input[type="number"] {
    padding: 0.4rem;
    border: 1px solid #d1d5db;
    border-radius: 8px;
    font-size: 0.9rem;
}

button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 500;
    transition: background-color 0.2s;
}

button:hover {
    background-color: #2563eb;
}

.danger-btn {
    background-color: #ef4444;
}

.danger-btn:hover {
    background-color: #dc2626;
}

.status {
    margin-left: auto;
    font-size: 0.9rem;
    color: #6b7280;
}

/* Main Layout */
main {
    flex: 1;
    overflow: hidden; /* 내부 스크롤을 위해 main은 hidden */
    padding: 1.5rem;
}

.container {
    display: flex;
    gap: 1.5rem;
    height: 100%;
    max-width: 1600px;
    margin: 0 auto;
}

.panel {
    flex: 1;
    background-color: var(--panel-bg);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.panel-header {
    padding: 1rem;
    font-weight: bold;
    background-color: #f9fafb;
    border-bottom: 1px solid #e5e7eb;
    text-align: center;
}

.content-area {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
    scroll-behavior: smooth;
}

/* Content Styling */
.sentence-pair {
    display: flex;
    flex-direction: column; /* 모바일 대응 */
    margin-bottom: 1.5rem;
}

/* Original Text Style */
.origin-box {
    padding: 1rem;
    background-color: #eff6ff;
    border-left: 4px solid var(--primary-color);
    border-radius: 8px;
    margin-bottom: 0.5rem;
    line-height: 1.6;
    font-size: 1.1rem;
}

/* Input Area Style */
.input-box {
    width: 100%;
    padding: 1rem;
    border: 1px solid #d1d5db;
    border-radius: 8px;
    resize: none;
    font-family: inherit;
    font-size: 1.1rem;
    line-height: 1.6;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
    background-color: #fff;
}

.input-box:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.input-box.filled {
    background-color: #f0fdf4; /* 완료 시 연한 초록색 */
    border-color: #86efac;
}

/* Navigation Footer */
.navigation-bar {
    background-color: var(--panel-bg);
    padding: 1rem;
    display: flex;
    justify-content: center;
    gap: 2rem;
    border-top: 1px solid #e5e7eb;
}

.navigation-bar button {
    min-width: 120px;
    font-size: 1rem;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 8px;
}
::-webkit-scrollbar-track {
    background: #f1f1f1; 
}
::-webkit-scrollbar-thumb {
    background: #c1c1c1; 
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: #a8a8a8; 
}

/* Mobile Adjustments */
@media (max-width: 768px) {
    .container {
        flex-direction: column;
        height: auto;
    }
    
    main {
        overflow-y: auto;
    }
    
    .panel {
        min-height: 400px;
    }
}