body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    padding: 30px;
    background-color: #f8f9fa;
    color: #212529;
    line-height: 1.6;
}

h1 {
    text-align: center;
    color: #343a40;
    margin-bottom: 40px;
    font-weight: 300;
    font-size: 2.5em;
}

.container {
    display: flex;
    justify-content: space-between;
    gap: 30px;
    margin-bottom: 30px;
}

.input-panel {
    flex: 1;
    background-color: #ffffff;
    padding: 25px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.07);
    border: 1px solid #dee2e6;
}

.input-panel h2 {
    margin-top: 0;
    font-size: 1.25em;
    color: #495057;
    border-bottom: 1px solid #e9ecef;
    padding-bottom: 10px;
    margin-bottom: 20px;
    font-weight: 500;
}

textarea {
    width: 100%;
    box-sizing: border-box;
    padding: 12px;
    border: 1px solid #ced4da;
    border-radius: 6px;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, Courier, monospace;
    font-size: 0.9em;
    resize: vertical;
    min-height: 250px;
    line-height: 1.5;
}

textarea:focus {
    outline: none;
    border-color: #80bdff;
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

button#diffButton {
    display: block;
    margin: 30px auto;
    padding: 12px 30px;
    font-size: 1.1em;
    font-weight: 500;
    cursor: pointer;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 6px;
    transition: background-color 0.2s ease, transform 0.1s ease;
    box-shadow: 0 2px 5px rgba(0,0,0,0.15);
}

button#diffButton:hover {
    background-color: #0056b3;
    transform: translateY(-1px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.15);
}

button#diffButton:active {
    transform: translateY(0px);
    box-shadow: 0 1px 3px rgba(0,0,0,0.15);
}

.options {
    text-align: center;
    margin-bottom: 30px;
    font-size: 0.95em;
    color: #495057;
}

.options label {
    cursor: pointer;
    margin-left: 5px;
}

.options input[type="checkbox"] {
    margin-right: 8px;
    vertical-align: middle;
    transform: scale(1.1);
}

.diff-output {
    background-color: #ffffff;
    padding: 25px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.07);
    margin-top: 30px;
    border: 1px solid #dee2e6;
}

.diff-output h2 {
    margin-top: 0;
    font-size: 1.25em;
    color: #495057;
    border-bottom: 1px solid #e9ecef;
    padding-bottom: 10px;
    margin-bottom: 20px;
    font-weight: 500;
    text-align: center;
}

/* Side-by-Side Diff Container Styling */
.diff-container {
    display: flex;
    flex-direction: row; /* Explicitly set row direction */
    gap: 0; /* No gap, border handles separation */
    border: 1px solid #dee2e6; /* Border around the whole diff */
    border-radius: 6px;
    overflow: hidden; /* Ensure child borders don't overlap */
    background-color: #f8f9fa; /* Background for the container */
    width: 100%; /* Ensure full width */
}

.diff-pane {
    flex: 1 1 50%; /* Each pane takes half the space, allows shrinking */
    display: flex; /* Use flex for line numbers + content */
    flex-direction: row; /* Explicitly set row direction */
    background-color: #ffffff; /* Pane background */
    min-width: 0; /* Prevent flex item overflow */
    max-width: 50%; /* Ensure each pane is exactly half */
}

/* Add border between panes */
.diff-pane#left-pane {
    border-right: 1px solid #dee2e6;
}

.diff-pane h3 {
    display: none; /* Hide the Original/Changed H3, use main H2 */
}

.linenumbers {
    background-color: #e9ecef; /* Slightly darker grey background for numbers */
    padding: 10px 8px;
    text-align: right;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, Courier, monospace;
    font-size: 0.85em;
    color: #6c757d; /* Dimmer color for numbers */
    user-select: none; /* Prevent selecting line numbers */
    white-space: pre; /* Keep line breaks */
    flex-shrink: 0; /* Prevent line numbers from shrinking */
    border-right: 1px solid #dee2e6; /* Separator line */
}

.linenumbers div {
    min-height: 1.5em; /* Match pre line-height */
    line-height: 1.5;  /* Match pre line-height */
    box-sizing: border-box; /* Include padding/border in height */
}

/* Style the <pre> elements within the panes */
.diff-pane pre {
    flex-grow: 1;
    margin: 0;
    padding: 10px 12px;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, Courier, monospace;
    white-space: pre-wrap;
    word-wrap: break-word;
    font-size: 0.9em;
    line-height: 1.5;
    color: #212529;
    background-color: #ffffff;
    border: none;
    border-radius: 0;
    overflow-x: auto; /* Add scrollbars if content overflows */
    box-sizing: border-box;
}

/* Styling for placeholder, inserted, deleted lines within pre */
.diff-pane pre div {
    min-height: 1.5em; /* Ensure empty lines take up space */
    line-height: 1.5;  /* Ensure alignment */
    box-sizing: border-box;
    width: 100%; /* Ensure background colors span full width */
    padding: 0 2px; /* Small horizontal padding for highlights */
    margin: 0 -2px; /* Counteract padding to align text */
}

.diff-placeholder {
    background-color: #f8f9fa; /* Subtle background for empty space */
}

.linenumbers .diff-placeholder {
    background-color: #e9ecef; /* Match line number background */
    color: transparent; /* Hide line number */
}

.diff-deleted {
    background-color: #ffe3e6; /* Lighter red background for the line */
}

.linenumbers .diff-deleted {
     background-color: #f8d7da; /* Slightly darker red for line number background */
}

.diff-inserted {
    background-color: #d4edda; /* Lighter green background for the line */
}

.linenumbers .diff-inserted {
     background-color: #c3e6cb; /* Slightly darker green for line number background */
}

/* Character-level diff styling */
ins {
    background-color: #a6f5b4; /* More vibrant green */
    color: #155724;
    text-decoration: none;
    /* padding: 0.1em 0; /* Minimal vertical padding */
    border-radius: 3px;
}

del {
    background-color: #f5a6b4; /* More vibrant red */
    color: #721c24;
    text-decoration: line-through;
    /* padding: 0.1em 0; */
    border-radius: 3px;
}