/* Basic Reset / Defaults */
*, *::before, *::after {
    box-sizing: border-box;
}

html {
    scroll-padding-top: 120px; /* Adjust based on sticky header height */
    /* Helps prevent content jumping behind sticky header on hash links */
}

body {
    margin: 0;
    padding: 0;
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

/* CSS Variables Definition */
:root {
    /* Light Theme (Default) */
    --bg-color: #f8f9fa;
    --text-color: #212529;
    --heading-color: #000000;
    --border-color: #dee2e6;
    --link-color: #007bff;
    --link-hover-color: #0056b3;
    --primary-accent: steelblue;
    --sticky-bg-color: rgba(248, 249, 250, 0.95); /* Slightly transparent */

    --table-header-bg: #e9ecef;
    --table-header-text: #495057;
    --table-row-bg: #ffffff;
    --table-border: #dee2e6;

    --chart-bg: #ffffff;
    --chart-axis-color: #495057;
    --chart-line-color: var(--primary-accent);
    --chart-border-color: var(--border-color);
    --chart-title-color: var(--heading-color);

    --tooltip-bg: rgba(255, 255, 255, 0.95);
    --tooltip-border: #cccccc;
    --tooltip-text: #333333;

    --button-bg: #e7e7e7;
    --button-text: #333333;
    --button-hover-bg: #dcdcdc;
    --button-preset-bg: #007bff;
    --button-preset-text: #ffffff;
    --button-preset-hover-bg: #0056b3;

    --font-primary: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';

    /* Chart Size Control - Using min-width for Grid */
    --chart-min-width: 280px; /* Default min width for grid items */
}

.dark-theme {
    /* Dark Theme Overrides */
    --bg-color: #212529;
    --text-color: #dee2e6;
    --heading-color: #ffffff;
    --border-color: #495057;
    --link-color: #6cb2eb;
    --link-hover-color: #8ec4f0;
    --primary-accent: lightskyblue;
    --sticky-bg-color: rgba(33, 37, 41, 0.95); /* Slightly transparent dark */

    --table-header-bg: #343a40;
    --table-header-text: #e9ecef;
    --table-row-bg: #2c3034;
    --table-border: #495057;

    --chart-bg: #2c3034;
    --chart-axis-color: #adb5bd;
    --chart-line-color: var(--primary-accent);
    --chart-border-color: var(--border-color);
    --chart-title-color: var(--heading-color);

    --tooltip-bg: rgba(40, 40, 40, 0.95);
    --tooltip-border: #666666;
    --tooltip-text: #e0e0e0;

    --button-bg: #495057;
    --button-text: #e0e0e0;
    --button-hover-bg: #5a6268;
    --button-preset-bg: #0056b3;
    --button-preset-text: #ffffff;
    --button-preset-hover-bg: #004494;
}

/* Apply Base Styles */
body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: var(--font-primary);
}

/* Sticky Top Bar Wrapper */
.sticky-top-bar {
    position: sticky;
    top: 0;
    z-index: 100; /* Ensure it's above other content */
    background-color: var(--sticky-bg-color); /* Use semi-transparent bg */
    backdrop-filter: blur(5px); /* Optional: nice blur effect */
    -webkit-backdrop-filter: blur(5px);
    box-shadow: 0 2px 4px rgba(0,0,0,0.1); /* Subtle shadow for separation */
    border-bottom: 1px solid var(--border-color); /* Fallback if shadow doesn't render */
}
/* Dark theme shadow */
.dark-theme .sticky-top-bar {
    box-shadow: 0 2px 4px rgba(0,0,0,0.3);
}


/* Header and Nav Styles (inside sticky wrapper) */
header, nav#controls {
    padding: 10px 20px; /* Reduced padding for thinner look */
    max-width: 1400px;
    margin: 0 auto;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color); /* Separator within sticky bar */
    padding-bottom: 8px; /* Space below header content */
}
header h1 {
    font-size: 1.5em; /* Reduced size */
    margin: 0; /* Remove margins */
}

nav#controls {
    padding-top: 8px; /* Space above nav content */
    padding-bottom: 12px; /* Space below nav content */
    border-bottom: none; /* Remove double border */
    display: flex;
    flex-wrap: wrap;
    gap: 15px 30px; /* Reduced gap */
    align-items: flex-end; /* Align items to bottom */
}

/* Main content needs padding so it doesn't start under the sticky header */
/* Adjust padding-top based on the actual height of your sticky header */
main {
     padding: 20px;
     max-width: 1400px;
     margin: 0 auto;
     /* scroll-margin-top: 130px; Add space above sections for anchor links */
}


h1, h2, h3 {
    color: var(--heading-color);
    margin-top: 1em;
    margin-bottom: 0.5em;
}
h2 { font-size: 1.4em; }
h3 { font-size: 1.0em; font-weight: bold; } /* Adjusted control group heading */

a { color: var(--link-color); text-decoration: none; }
a:hover { color: var(--link-hover-color); text-decoration: underline; }

/* Button Styles */
button {
    background-color: var(--button-bg); color: var(--button-text);
    border: 1px solid var(--border-color); padding: 6px 12px; /* Slightly smaller */
    border-radius: 4px; cursor: pointer; font-size: 0.85em; /* Smaller font */
    transition: background-color 0.2s, border-color 0.2s;
}
button:hover { background-color: var(--button-hover-bg); }

#theme-toggle {
    background: none; border: none; font-size: 1.6em;
    cursor: pointer; padding: 0 5px; line-height: 1;
}

/* Control Section Styles */
.control-group { /* No specific styles needed now */ }
.control-group h3 {
    margin-top: 0; margin-bottom: 8px;
    font-size: 1.0em; border-bottom: none; padding-bottom: 0;
    color: var(--heading-color); opacity: 0.9;
}

#date-picker label { margin-right: 5px; font-weight: normal; font-size: 0.85em;}
#date-picker input[type="datetime-local"] {
    margin-right: 10px; padding: 4px; border: 1px solid var(--border-color);
    background-color: var(--bg-color); color: var(--text-color);
    border-radius: 3px; font-size: 0.85em;
}
#time-presets { margin-top: 5px; }
#time-presets .preset-button {
    margin-right: 8px; margin-bottom: 5px;
    background-color: var(--button-preset-bg); color: var(--button-preset-text);
    border-color: var(--button-preset-bg);
}
#time-presets .preset-button:hover {
    background-color: var(--button-preset-hover-bg); border-color: var(--button-preset-hover-bg);
}

/* Chart Size Slider Controls */
.control-group label[for="chart-size-slider"] { margin-right: 5px; font-size: 0.85em;}
#chart-size-slider {
    vertical-align: middle; margin: 0 8px 0 0;
    width: 120px; /* Smaller slider */ cursor: pointer;
}
#chart-size-value {
    display: inline-block; min-width: 45px; /* Adjusted width */
    text-align: right; font-weight: bold; vertical-align: middle;
    font-family: monospace; font-size: 0.85em;
}

/* Main Content Sections */
main section { margin-bottom: 30px; }

/* Latest Reading Table */
#latest-reading-container { overflow-x: auto; }
#latest-reading-table {
     width: 100%; border-collapse: collapse; margin-top: 10px;
     border: 1px solid var(--table-border);
}
#latest-reading-table th, #latest-reading-table td {
    padding: 8px 12px; text-align: left; font-size: 0.9em;
    border-bottom: 1px solid var(--table-border);
}
#latest-reading-table th {
    background-color: var(--table-header-bg); font-weight: bold;
    color: var(--table-header-text); border-bottom: 2px solid var(--table-border);
}
#latest-reading-table td { background-color: var(--table-row-bg); }

/* Charts Area - Using CSS Grid */
#charts-container {
    display: grid;
    /* Use the CSS variable for min width, default set in :root */
    /* auto-fit: fit as many columns as possible */
    /* minmax(): each column is at least --chart-min-width wide, and max 1fr (share remaining space) */
    grid-template-columns: repeat(auto-fit, minmax(var(--chart-min-width), 1fr));
    gap: 20px; /* Gap between grid items */
}

.chart {
    /* Grid items automatically fill the cell */
    position: relative; /* For absolute tooltip positioning */
    background-color: var(--chart-bg);
    border: 1px solid var(--chart-border-color);
    border-radius: 5px;
    padding: 15px;
    min-height: 300px; /* Prevent collapse when empty/loading */
    /* Removed flex properties and max-width */
    width: 100%; /* Fill grid column width */
}

/* Chart SVG Styling */
.chart svg {
    display: block; width: 100%; height: auto; max-width: 100%;
}
.axis path, .axis line { fill: none; stroke: var(--chart-axis-color); shape-rendering: crispEdges; stroke-width: 1px; }
.axis text { fill: var(--chart-axis-color); font-size: 0.8em; }
.axis-label { fill: var(--chart-axis-color); font-size: 0.9em; font-weight: bold; }
.line { fill: none; stroke: var(--chart-line-color); stroke-width: 1.5px; } /* Slightly thinner line */

.chart-title {
     text-align: center; font-weight: bold; margin-top: 0;
     margin-bottom: 10px; font-size: 1.0em; /* Slightly smaller title */
     color: var(--chart-title-color);
}

/* Tooltip */
.tooltip {
     position: absolute; background-color: var(--tooltip-bg); padding: 8px 12px;
     border: 1px solid var(--tooltip-border); border-radius: 4px;
     pointer-events: none; font-size: 0.9em; color: var(--tooltip-text);
     text-align: left; line-height: 1.5em; opacity: 0;
     transition: opacity 0.2s; z-index: 10; white-space: nowrap;
}

/* Loading/Error Message Styles */
.loading-message, .error-message, .no-data-message {
    padding: 20px; text-align: center; color: var(--text-color); opacity: 0.8; font-size: 0.9em;
}
.error-message { color: #dc3545; font-weight: bold; }
.dark-theme .error-message { color: #f8d7da; }

/* Footer Styles */
footer {
    margin-top: 40px; padding: 15px 20px; /* Consistent padding */
    border-top: 1px solid var(--border-color); text-align: center;
    font-size: 0.85em; color: var(--text-color); opacity: 0.7;
    max-width: 1400px; margin: 40px auto 0 auto; /* Center footer */
}

/* Utility class */
.visually-hidden { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }

/* Responsive Adjustments */
@media (max-width: 768px) {
    html { scroll-padding-top: 100px; } /* Adjust if header height changes */
    header, nav#controls { padding: 8px 15px; }
    header h1 { font-size: 1.3em; }
    nav#controls { gap: 10px 15px; }
    #date-picker { display: flex; flex-direction: column; gap: 5px; }
    #date-picker label { margin-right: 0; }
    #date-picker input[type="datetime-local"] { margin-right: 0; width: 100%; }
    .chart { padding: 10px; min-height: 250px; } /* Adjust padding */
    #latest-reading-table th, #latest-reading-table td { padding: 6px 8px; font-size: 0.85em; }
    footer { font-size: 0.8em; margin-top: 20px; }
}
@media (max-width: 480px) {
    .control-group { width: 100%; /* Stack control groups */ }
    #time-presets .preset-button { width: calc(50% - 5px); margin-right: 5px; } /* Two buttons per row */
    #time-presets .preset-button:nth-child(even) { margin-right: 0; }
    .chart { /* Grid already handles wrapping */ }
}