:root {
    --primary-color: #4a6fa5;
    --primary-dark: #3a5a8c;
    --secondary-color: #61b15a;
    --accent-color: #ffce56;
    --text-color: #333;
    --text-secondary: #666;
    --background-color: #f8f9fa;
    --card-bg: #ffffff;
    --border-color: #e0e0e0;
    --error-color: #d9534f;
    --success-color: #5cb85c;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --border-radius: 8px;
    --font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, 'Roboto', Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;
}

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

body {
    font-family: var(--font-family);
    line-height: 1.6;
    background-color: var(--background-color);
    color: var(--text-color);
}

.app-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 30px;
    padding: 20px 0;
}

h1 {
    color: var(--primary-color);
    font-size: 2.5rem;
    margin-bottom: 5px;
}

.tagline {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Tabs */
.tabs {
    display: flex;
    justify-content: center;
    margin-bottom: 20px;
    border-bottom: 2px solid var(--border-color);
}

.tab-btn {
    padding: 10px 20px;
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    color: var(--text-secondary);
    transition: all 0.3s ease;
    position: relative;
}

.tab-btn:hover {
    color: var(--primary-color);
}

.tab-btn.active {
    color: var(--primary-color);
    font-weight: 600;
}

.tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--primary-color);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

/* Cards */
.card {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
}

h2 {
    color: var(--primary-color);
    margin-bottom: 20px;
    font-size: 1.8rem;
}

h3 {
    color: var(--text-color);
    margin-bottom: 15px;
    font-size: 1.4rem;
}

/* Forms */
.form-group {
    margin-bottom: 20px;
}

label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
}

input[type="date"],
input[type="number"],
textarea {
    width: 100%;
    padding: 12px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    font-family: var(--font-family);
    font-size: 1rem;
}

input[type="date"]:focus,
input[type="number"]:focus,
textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.meal-sections {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

/* Buttons */
.btn {
    padding: 12px 24px;
    border-radius: var(--border-radius);
    border: none;
    cursor: pointer;
    font-weight: 600;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.primary-btn {
    background-color: var(--primary-color);
    color: white;
}

.primary-btn:hover {
    background-color: var(--primary-dark);
}

.secondary-btn {
    background-color: white;
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
}

.secondary-btn:hover {
    background-color: #f0f5ff;
}

.text-btn {
    background: none;
    color: var(--primary-color);
    padding: 12px 16px;
}

.text-btn:hover {
    text-decoration: underline;
}

.btn-group {
    display: flex;
    gap: 15px;
    margin-top: 15px;
}

/* Tables */
.table-container {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
}

th, td {
    padding: 12px 15px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

th {
    background-color: #f8f9fa;
    font-weight: 600;
    color: var(--text-secondary);
}

/* Chart */
.chart-container {
    width: 100%;
    height: 400px;
    margin-top: 20px;
}

.chart-filters {
    display: flex;
    align-items: end;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 20px;
}

.chart-filters .form-group {
    margin-bottom: 0;
    min-width: 180px;
}

.placeholder-message {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    color: var(--text-secondary);
    font-style: italic;
}

/* File Input */
.file-input-container {
    display: flex;
    align-items: center;
    margin-bottom: 15px;
}

input[type="file"] {
    position: absolute;
    left: -9999px;
}

#file-name-display {
    margin-left: 15px;
    color: var(--text-secondary);
}

.import-options {
    margin-bottom: 20px;
}

.radio-container {
    display: flex;
    align-items: center;
    margin-bottom: 10px;
    cursor: pointer;
}

.radio-text {
    margin-left: 10px;
}

/* Features list */
.features-list {
    list-style-type: none;
    margin: 15px 0;
}

.features-list li {
    padding: 5px 0;
    position: relative;
    padding-left: 25px;
}

.features-list li::before {
    content: '✓';
    color: var(--secondary-color);
    position: absolute;
    left: 0;
}

/* Footer */
footer {
    text-align: center;
    padding: 20px 0;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
    .tabs {
        flex-wrap: wrap;
    }
    
    .tab-btn {
        flex: 1 0 auto;
        padding: 10px;
        font-size: 0.9rem;
    }
    
    .card {
        padding: 15px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
    
    .chart-filters {
        flex-direction: column;
        align-items: stretch;
    }
    
    .chart-filters .form-group {
        margin-bottom: 10px;
    }
    
    .btn {
        width: 100%;
        margin-bottom: 10px;
    }
    
    .btn-group {
        flex-direction: column;
    }
}