:root {
    --primary-color: #1A237E;
    --secondary-color: #5C6BC0;
    --accent-color: #FFCA28;
    --background-color: #F5F5F5;
    --text-color: #333333;
    --card-bg-color: #FFFFFF;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: 'Noto Sans KR', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
}

header {
    background-color: var(--primary-color);
    color: white;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 4px var(--shadow-color);
}

header h1 {
    font-size: 1.5rem;
    display: flex;
    align-items: center;
}

header h1 i {
    margin-right: 0.75rem;
}

.file-controls {
    display: flex;
    gap: 0.8rem;
}

.file-button {
    background-color: var(--accent-color);
    color: var(--primary-color);
    padding: 0.6rem 1rem;
    border-radius: 5px;
    cursor: pointer;
    font-weight: 500;
    transition: background-color 0.3s ease;
    border: none;
    font-family: 'Noto Sans KR', sans-serif;
    font-size: 0.9rem;
}

.file-button:hover {
    background-color: #ffd860;
}

#download-sample {
    background-color: #5C6BC0;
    color: white;
}
#download-sample:hover {
    background-color: #7986CB;
}

.file-button i {
    margin-right: 0.5rem;
}

#file-upload {
    display: none;
}

nav {
    display: flex;
    background-color: var(--card-bg-color);
    box-shadow: 0 2px 4px var(--shadow-color);
}

.tab-button {
    flex-grow: 1;
    padding: 1rem;
    font-size: 1rem;
    font-weight: 500;
    background-color: transparent;
    border: none;
    border-bottom: 3px solid transparent;
    cursor: pointer;
    transition: all 0.3s ease;
    color: var(--secondary-color);
}

.tab-button i {
    margin-right: 0.5rem;
}

.tab-button:hover {
    background-color: #f0f0f0;
    color: var(--primary-color);
}

.tab-button.active {
    color: var(--primary-color);
    border-bottom: 3px solid var(--primary-color);
}

main {
    padding: 2rem;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.5s;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Card styles for dashboard items */
.card {
    background-color: var(--card-bg-color);
    border-radius: 8px;
    box-shadow: 0 4px 8px var(--shadow-color);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.card h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    border-bottom: 2px solid var(--background-color);
    padding-bottom: 0.5rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    header {
        flex-direction: column;
        padding: 1rem;
        gap: 1rem;
    }

    .file-controls {
        width: 100%;
        justify-content: center;
    }

    nav {
        flex-direction: column;
    }

    .tab-button {
        border-bottom: 1px solid #ddd;
    }

    .tab-button.active {
        border-bottom: 3px solid var(--primary-color);
    }

    main {
        padding: 1rem;
    }
}