* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', 'Malgun Gothic', '맑은 고딕', sans-serif;
    min-height: 100vh;
    padding: 20px;
    color: #333;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    border-radius: 20px;
    overflow: hidden;
}

header {
    color: #333;
    padding: 40px;
    text-align: center;
}

header h1 {
    font-size: 2.5em;
    margin-bottom: 10px;
    font-weight: 700;
}

.subtitle {
    font-size: 1.1em;
    opacity: 0.95;
}

main {
    padding: 40px;
}

.converter-container {
    display: grid;
    gap: 30px;
    margin-bottom: 40px;
}

.input-section,
.output-section {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

label {
    font-size: 1.1em;
    font-weight: 600;
    color: #000;
}

textarea {
    width: 100%;
    padding: 15px;
    border: 2px solid #e0e0e0;
    border-radius: 10px;
    font-size: 1em;
    font-family: 'Malgun Gothic', '맑은 고딕', sans-serif;
    resize: vertical;
    transition: border-color 0.3s ease;
}

textarea:focus {
    outline: none;
    border-color: #000;
}

textarea[readonly] {
    background-color: #f9f9f9;
}

.button-container {
    display: flex;
    gap: 15px;
    justify-content: center;
}

.convert-btn,
.clear-btn,
.copy-btn {
    border: none;
    border-radius: 20px;
    padding: 10px 20px;
    margin: 20px 0;
    width: 400px;
    height: 51px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
    cursor: pointer;
    transition: background-color 0.3s ease, transform 0.1s ease, box-shadow 0.3s ease;
    font-weight: bold;
    font-size: 25px;
}

.convert-btn {
    background: #007BFF;
    color: white;
}

.convert-btn:hover {
    transform: translateY(2px);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    background: #005BDD;
}

.convert-btn:active {
    background: #0026a3;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.convert-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.clear-btn {
    background: #f0f0f0;
    color: #666;
}

.clear-btn:hover {
    background: #e0e0e0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    transform: translateY(2px);
}

.clear-btn:active {
    background: #2d8031;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.clear-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.copy-btn {
    background: #4CAF50;
    color: white;
    margin-top: 10px;
    width: 100%;
}

.copy-btn:hover {
    background: #45a049;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    transform: translateY(2px);
}


footer {
    background: #f8f9fa;
    text-align: center;
    padding: 20px;
    color: #666;
    font-size: 0.9em;
}

.btn-loader {
    display: inline-block;
}

@media (max-width: 768px) {
    body {
        padding: 10px;
    }

    header h1 {
        font-size: 1.8em;
    }

    main {
        padding: 20px;
    }

    .button-container {
        flex-direction: column;
    }

    .convert-btn,
    .clear-btn {
        width: 100%;
    }
}

.error-message {
    background: #fee;
    color: #c33;
    padding: 15px;
    border-radius: 10px;
    margin-top: 15px;
    border-left: 4px solid #c33;
}

.success-message {
    background: #efe;
    color: #3c3;
    padding: 10px;
    border-radius: 5px;
    margin-top: 5px;
    text-align: center;
    font-size: 0.9em;
}