src/style.css

:root {
    --primary-color: #60a5fa;
    --secondary-color: #94a3b8;
    --success-color: #34d399;
    --warning-color: #fbbf24;
    --danger-color: #f87171;
    --bg-color: #1e1e1e;
    --card-bg: #2d2d2d;
    --text-color: #e5e7eb;
    --border-color: #404040;
    --optimal-color: rgba(52, 211, 153, 0.2);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

#app {
    min-height: 100vh;
    display: block;
}

header {
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 2rem;
    flex-wrap: wrap;
}

.header-title {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.header-icon {
    width: 64px;
    height: 64px;
    object-fit: contain;
}

header h1 {
    font-size: 1.5rem;
    color: var(--primary-color);
    font-weight: 700;
    white-space: nowrap;
}

.header-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.help-button {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background-color: var(--primary-color);
    color: white;
    border: none;
    font-size: 1.25rem;
    font-weight: bold;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.2s, transform 0.2s;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.help-button:hover {
    background-color: #1d4ed8;
    transform: scale(1.05);
}

.help-popover {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: 1rem;
}

.help-popover.hidden {
    display: none;
}

.help-popover-content {
    background-color: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    max-width: 700px;
    max-height: 90vh;
    overflow-y: auto;
    position: relative;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.help-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: none;
    font-size: 2rem;
    color: var(--secondary-color);
    cursor: pointer;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 4px;
    transition: background-color 0.2s, color 0.2s;
}

.help-close:hover {
    background-color: var(--bg-color);
    color: var(--text-color);
}

.help-popover-content h2 {
    margin-bottom: 1.5rem;
    color: var(--primary-color);
    font-size: 1.5rem;
}

.help-section {
    margin-bottom: 1.5rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.help-section:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.help-section h3 {
    color: var(--text-color);
    font-size: 1.125rem;
    margin-bottom: 0.5rem;
    font-weight: 600;
}

.help-section p {
    color: var(--secondary-color);
    line-height: 1.6;
    margin-bottom: 0.75rem;
}

.help-section ul {
    margin-left: 1.5rem;
    color: var(--secondary-color);
}

.help-section li {
    margin-bottom: 0.5rem;
    line-height: 1.5;
}

.help-section strong {
    color: var(--text-color);
    font-weight: 600;
}

.activity-popover {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: 1rem;
}

.activity-popover.hidden {
    display: none;
}

.activity-popover-content {
    background-color: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    width: 90%;
    max-width: 1200px;
    max-height: 90vh;
    overflow-y: auto;
    position: relative;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

#activity-date-title {
    margin-bottom: 1.5rem;
    color: var(--primary-color);
    font-size: 1.5rem;
}

#activity-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.activity-item {
    background-color: var(--bg-color);
    border-radius: 8px;
    padding: 1.25rem;
    border-left: 4px solid var(--primary-color);
}

.activity-item-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-color);
}

.activity-item-details {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    font-size: 0.875rem;
}

.activity-detail {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.activity-detail-label {
    color: var(--secondary-color);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.activity-detail-value {
    color: var(--text-color);
    font-weight: 600;
    font-size: 1.125rem;
}

main {
    padding: 2rem;
    max-width: 100%;
    margin: 0 auto;
    width: 100%;
}

section {
    margin-bottom: 2rem;
}

h2 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-color);
    font-weight: 600;
}

.hidden {
    display: none;
}

/* Upload Section */
#upload-section {
    background-color: var(--card-bg);
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.upload-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.ftp-input-container {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 0.75rem;
    background-color: var(--bg-color);
    border-radius: 6px;
    border: 1px solid var(--border-color);
}

.ftp-input-container label {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-color);
    white-space: nowrap;
}

#ftp-input,
#target-acwr-input,
#threshold-hr-input,
#resting-hr-input {
    width: 70px;
    padding: 0.375rem 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    font-size: 0.875rem;
    text-align: center;
    background-color: #3a3a3a;
    color: var(--text-color);
}

#ftp-input:focus,
#target-acwr-input:focus,
#threshold-hr-input:focus,
#resting-hr-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(96, 165, 250, 0.2);
}

.ftp-unit {
    font-size: 0.75rem;
    color: var(--secondary-color);
    font-weight: 500;
}

#csv-upload {
    display: none;
}

.upload-label {
    display: inline-block;
    padding: 0.5rem 1rem;
    background-color: var(--primary-color);
    color: white;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    font-size: 0.875rem;
    transition: background-color 0.2s;
    white-space: nowrap;
}

.upload-label:hover {
    background-color: #1d4ed8;
}

#upload-status {
    font-size: 0.875rem;
    color: var(--secondary-color);
    min-height: 1.5rem;
    max-width: 100%;
    white-space: pre-wrap;
    text-align: left;
    margin-bottom: 1rem;
}

#upload-status.success {
    color: var(--success-color);
    font-weight: 500;
}

#upload-status.error {
    color: var(--danger-color);
    font-weight: 500;
    background-color: #fef2f2;
    border: 1px solid #fecaca;
    border-radius: 6px;
    padding: 1rem;
    line-height: 1.6;
}

/* Filter Section */
#filter-section {
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 200;
}

#filter-container {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 1.5rem;
    max-width: 100%;
    margin: 0 auto;
}

.filter-checkbox {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 1rem;
    user-select: none;
    padding: 0.5rem 0.75rem;
    border-radius: 6px;
    transition: background-color 0.2s;
}

.filter-checkbox:hover {
    background-color: var(--bg-color);
}

.filter-checkbox input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.filter-checkbox span {
    font-weight: 500;
    color: var(--text-color);
}

/* Charts Section */
#charts-section {
    display: grid;
    gap: 2rem;
    grid-template-columns: 1fr;
}

/* Two-column layout for desktop */
@media (min-width: 1400px) {
    #charts-section {
        grid-template-columns: repeat(2, 1fr);
    }
}

.chart-container {
    background-color: #00000075;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
}

.chart-container h2 {
    color: #fbfefe;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.acwr-display {
    font-size: 0.85em;
    font-weight: normal;
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
}

.acwr-display span:first-child {
    padding: 0.2rem 0.6rem;
    border-radius: 6px;
    border: 2px solid currentColor;
    background: rgba(0, 0, 0, 0.2);
    font-weight: 600;
    letter-spacing: 0.02em;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.chart-container canvas {
    max-height: 400px;
    width: 100%;
}

.target-info {
    background-color: var(--bg-color);
    border-left: 4px solid var(--primary-color);
    padding: 0.75rem 1rem;
    margin-bottom: 1rem;
    border-radius: 4px;
    font-size: 0.875rem;
    color: var(--text-color);
    display: none;
}

.target-info.visible {
    display: block;
}

.target-info strong {
    color: var(--primary-color);
    font-weight: 600;
}

.target-info .target-value {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--primary-color);
}

/* Legend */
.legend {
    margin-top: 1rem;
    display: flex;
    gap: 1.5rem;
    flex-wrap: wrap;
    grid-column: 1 / -1;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
}

.legend-color {
    width: 20px;
    height: 20px;
    border-radius: 4px;
}

.legend-color.low {
    background-color: rgba(59, 130, 246, 0.3);
    border: 2px solid rgba(59, 130, 246, 0.9);
}

.legend-color.optimal {
    background-color: rgba(16, 185, 129, 0.3);
    border: 2px solid rgba(16, 185, 129, 0.9);
}

.legend-color.warning {
    background-color: hsl(40deg 95% 53% / 30%);
    border: 2px solid hsl(40deg 95% 53% / 90%);
}

.legend-color.high {
    background-color: rgba(239, 68, 68, 0.3);
    border: 2px solid rgba(239, 68, 68, 0.9);
}

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

    header h1 {
        font-size: 1.25rem;
    }

    main {
        padding: 1rem;
    }

    h2 {
        font-size: 1.25rem;
    }

    #upload-section {
        padding: 1.5rem;
    }

    .chart-container {
        padding: 1rem;
    }
}