* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: #f4f6f9;
    color: #333;
    line-height: 1.6;
    padding: 20px;
}
.container {
    max-width: 700px;
    margin: 40px auto;
    background: #fff;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
}
header {
    text-align: center;
    margin-bottom: 30px;
    border-bottom: 1px solid #eaeaea;
    padding-bottom: 20px;
}
header h1 {
    color: #2c3e50;
    font-size: 24px;
    margin-bottom: 8px;
}
header p {
    color: #7f8c8d;
    font-size: 14px;
}
.tool-section {
    margin-bottom: 30px;
    padding: 20px;
    background: #fdfdfd;
    border: 1px solid #f0f0f0;
    border-radius: 6px;
}
.tool-section h2 {
    font-size: 18px;
    color: #34495e;
    margin-bottom: 15px;
}
.control-group {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 15px;
}
input[type="number"], input[type="text"], textarea {
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 4px;
    font-size: 14px;
}
input[type="number"] {
    width: 70px;
}
textarea {
    width: 100%;
    height: 100px;
    resize: vertical;
    margin-bottom: 15px;
}
.output-group {
    display: flex;
    gap: 10px;
}
.output-group input {
    flex: 1;
    background: #f9f9f9;
    font-family: monospace;
}
button {
    padding: 10px 18px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 500;
    font-size: 14px;
    transition: background 0.2s;
}
.btn-primary { background: #3498db; color: #fff; }
.btn-primary:hover { background: #2980b9; }
.btn-secondary { background: #ecf0f1; color: #2c3e50; }
.btn-secondary:hover { background: #bdc3c7; }
.btn-danger { background: #e74c3c; color: #fff; }
.btn-danger:hover { background: #c0392b; }
.btn-group { display: flex; gap: 10px; }
footer {
    text-align: center;
    margin-top: 30px;
    font-size: 12px;
    color: #95a5a6;
}