:root {
    --bg: #f5f7fa;
    --card-bg: #ffffff;
    --text: #1a1a2e;
    --text-muted: #6b7280;
    --border: #e5e7eb;
    --primary: #2563eb;
    --primary-light: #dbeafe;
    --danger: #dc2626;
    --danger-light: #fef2f2;
    --warning: #f59e0b;
    --warning-light: #fffbeb;
    --success: #10b981;
    --success-light: #ecfdf5;
    --water: #3b82f6;
    --water-dark: #1d4ed8;
    --water-surface: #60a5fa;
    --radius: 12px;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #0f172a;
        --card-bg: #1e293b;
        --text: #f1f5f9;
        --text-muted: #94a3b8;
        --border: #334155;
        --primary-light: #1e3a5f;
        --danger-light: #3b1111;
        --warning-light: #3b2f11;
        --success-light: #113b2d;
        --water: #3b82f6;
        --water-dark: #2563eb;
        --water-surface: #60a5fa;
    }
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

/* ── Header ── */
header {
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    padding: 12px 20px;
    display: flex;
    align-items: center;
    gap: 10px;
}

header h1 { font-size: 17px; font-weight: 600; }
.header-link { color: inherit; text-decoration: none; }
.header-nav { margin-left: auto; }
.header-nav a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 13px;
}
.header-nav a:hover { color: var(--text); }

.status-dot {
    width: 8px; height: 8px;
    border-radius: 50%;
    background: var(--text-muted);
    flex-shrink: 0;
}
.status-dot.online { background: var(--success); }
.status-dot.warning { background: var(--warning); }
.status-dot.offline { background: var(--danger); }

main {
    max-width: 480px;
    margin: 0 auto;
    padding: 16px;
}

/* ── Alerts ── */
.banner {
    padding: 10px 14px;
    border-radius: 8px;
    margin-bottom: 10px;
    font-size: 13px;
    font-weight: 500;
}
.banner a { color: inherit; text-decoration: underline; }
.banner-warning { background: var(--warning-light); color: #92400e; border: 1px solid rgba(245,158,11,0.3); }
.banner-danger { background: var(--danger-light); color: #991b1b; border: 1px solid rgba(220,38,38,0.3); }
@media (prefers-color-scheme: dark) {
    .banner-warning { color: #fbbf24; }
    .banner-danger { color: #fca5a5; }
}

/* ── Dashboard grid (desktop side-by-side) ── */
.dashboard-grid {
    display: flex;
    flex-direction: column;
}

/* ── 3D Cylinder Tank ── */
.tank-section {
    display: flex;
    justify-content: center;
    padding: 24px 0 16px;
}

.tank-visual {
    text-align: center;
}

.cylinder {
    position: relative;
    width: 140px;
    margin: 0 auto;
}

/* Elliptical caps for 3D effect */
.cylinder-cap {
    width: 100%;
    height: 28px;
    border-radius: 50%;
    position: relative;
    z-index: 3;
}

.cylinder-cap-top {
    background: var(--card-bg);
    border: 3px solid var(--border);
    margin-bottom: -14px;
}

.cylinder-cap-bottom {
    background: var(--border);
    border: 3px solid var(--border);
    margin-top: -14px;
    z-index: 0;
}

.cylinder-body {
    width: 100%;
    height: 200px;
    border-left: 3px solid var(--border);
    border-right: 3px solid var(--border);
    position: relative;
    overflow: hidden;
    background: var(--card-bg);
}

/* Water fill */
.cylinder-water {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 0%;
    background: linear-gradient(180deg, var(--water) 0%, var(--water-dark) 100%);
    transition: height 1s ease-out;
}

/* Elliptical water surface cap */
.cylinder-water-cap {
    position: absolute;
    top: -10px;
    left: -3px;
    right: -3px;
    height: 22px;
    border-radius: 50%;
    background: var(--water-surface);
    opacity: 0.85;
    animation: water-bob 3s ease-in-out infinite alternate;
}

@keyframes water-bob {
    0% { transform: scaleY(0.85) translateY(1px); }
    100% { transform: scaleY(1.15) translateY(-1px); }
}

/* Vertical shine/reflection streak on cylinder */
.cylinder-shine {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 12%;
    width: 18%;
    background: linear-gradient(180deg, rgba(255,255,255,0.25) 0%, rgba(255,255,255,0.05) 100%);
    border-radius: 50% / 10%;
    pointer-events: none;
}

.cylinder-reflection {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 8%;
    width: 12%;
    background: linear-gradient(180deg, rgba(255,255,255,0.08) 0%, rgba(255,255,255,0.02) 100%);
    border-radius: 50% / 10%;
    pointer-events: none;
    z-index: 2;
}

/* Percent label centered on cylinder */
.cylinder-label {
    position: absolute;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 4;
    pointer-events: none;
}

.tank-percent {
    font-size: 42px;
    font-weight: 800;
    color: var(--text);
    text-shadow: 0 1px 4px rgba(0,0,0,0.15);
    line-height: 1;
}

.tank-percent small {
    font-size: 0.4em;
    font-weight: 600;
    vertical-align: super;
    opacity: 0.7;
}

/* White text when water is high */
.cylinder-body.high-water .tank-percent,
.cylinder-body.high-water .tank-percent small {
    color: white;
    text-shadow: 0 2px 8px rgba(0,0,0,0.35);
}

.tank-meta {
    margin-top: 16px;
}

.tank-volume {
    font-size: 18px;
    font-weight: 600;
}

.tank-level {
    font-size: 14px;
    color: var(--text-muted);
}

.tank-updated {
    font-size: 12px;
    color: var(--text-muted);
    margin-top: 2px;
}

/* ── Prediction bar ── */
.prediction-bar {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 12px 16px;
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 14px;
    font-weight: 500;
}

.prediction-bar.urgent { border-color: var(--danger); background: var(--danger-light); }
.prediction-bar.warn { border-color: var(--warning); background: var(--warning-light); }

.prediction-icon { font-size: 18px; flex-shrink: 0; }

/* ── Quick stats ── */
.quick-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    margin-bottom: 16px;
}

.stat {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 10px 8px;
    text-align: center;
}

.stat-label {
    display: block;
    font-size: 10px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-muted);
}

.stat-value {
    display: block;
    font-size: 18px;
    font-weight: 700;
    line-height: 1.3;
    font-variant-numeric: tabular-nums;
}

.stat-unit {
    display: block;
    font-size: 10px;
    color: var(--text-muted);
}

/* ── Battery icon ── */
.battery-wrap {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 24px;
}

.battery-icon {
    display: inline-flex;
    align-items: center;
    gap: 0;
}

.battery-tip {
    width: 3px;
    height: 8px;
    background: var(--border);
    border-radius: 1px 1px 0 0;
    /* Rotated: tip is on the right side */
}

.battery-body {
    width: 28px;
    height: 16px;
    border: 2px solid var(--border);
    border-radius: 2px;
    position: relative;
    overflow: hidden;
    order: -1; /* body before tip */
}

.battery-fill {
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 0%;
    background: var(--success);
    transition: width 0.5s ease-out, background 0.3s;
    border-radius: 0;
}

/* Color thresholds */
.battery-icon.battery-low .battery-fill { background: var(--danger); }
.battery-icon.battery-low .battery-body { border-color: var(--danger); }
.battery-icon.battery-low .battery-tip { background: var(--danger); }

.battery-icon.battery-mid .battery-fill { background: var(--warning); }
.battery-icon.battery-mid .battery-body { border-color: var(--warning); }
.battery-icon.battery-mid .battery-tip { background: var(--warning); }

.battery-icon.battery-good .battery-fill { background: var(--success); }
.battery-icon.battery-good .battery-body { border-color: var(--success); }
.battery-icon.battery-good .battery-tip { background: var(--success); }

/* ── Signal strength bars ── */
.signal-bars-wrap {
    display: flex;
    justify-content: center;
    align-items: flex-end;
    min-height: 24px;
}

.signal-bars {
    display: inline-flex;
    align-items: flex-end;
    gap: 2px;
    height: 20px;
}

.signal-bar {
    width: 5px;
    border-radius: 1px;
    background: var(--border);
    transition: background 0.3s;
}

.signal-bar:nth-child(1) { height: 25%; }
.signal-bar:nth-child(2) { height: 50%; }
.signal-bar:nth-child(3) { height: 75%; }
.signal-bar:nth-child(4) { height: 100%; }

/* Signal levels: colored bars */
.signal-bars.signal-1 .signal-bar:nth-child(1) { background: var(--danger); }

.signal-bars.signal-2 .signal-bar:nth-child(1),
.signal-bars.signal-2 .signal-bar:nth-child(2) { background: var(--warning); }

.signal-bars.signal-3 .signal-bar:nth-child(1),
.signal-bars.signal-3 .signal-bar:nth-child(2),
.signal-bars.signal-3 .signal-bar:nth-child(3) { background: var(--success); }

.signal-bars.signal-4 .signal-bar:nth-child(1),
.signal-bars.signal-4 .signal-bar:nth-child(2),
.signal-bars.signal-4 .signal-bar:nth-child(3),
.signal-bars.signal-4 .signal-bar:nth-child(4) { background: var(--success); }

/* ── Expandable details ── */
.details-panel {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    margin-bottom: 10px;
    overflow: hidden;
}

.details-panel summary {
    padding: 12px 16px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    list-style: none;
    display: flex;
    align-items: center;
    justify-content: space-between;
    user-select: none;
}

.details-panel summary::-webkit-details-marker { display: none; }

.details-panel summary::after {
    content: '\25BC';
    font-size: 10px;
    color: var(--text-muted);
    transition: transform 0.2s;
}

.details-panel[open] summary::after {
    transform: rotate(180deg);
}

.details-content {
    padding: 0 16px 16px;
}

.detail-row {
    display: flex;
    justify-content: space-between;
    padding: 8px 0;
    border-bottom: 1px solid var(--border);
    font-size: 13px;
}

.detail-row:last-child { border-bottom: none; }
.detail-row span:last-child { font-weight: 500; font-variant-numeric: tabular-nums; }

/* Charts inside details */
.details-content h3 {
    font-size: 13px;
    font-weight: 600;
    margin: 16px 0 8px;
    color: var(--text-muted);
}

.details-content h3:first-child { margin-top: 0; }

.chart-wrap {
    position: relative;
    height: 200px;
    margin-bottom: 8px;
}

/* ── Settings page ── */
.settings-page { max-width: 500px; }

.device-list { margin-bottom: 20px; }

.device-item {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.device-item:hover { background: var(--primary-light); }

.form-group { margin-bottom: 14px; }
.form-group label {
    display: block;
    font-size: 13px;
    font-weight: 500;
    margin-bottom: 4px;
}

.form-group input {
    width: 100%;
    padding: 8px 10px;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 14px;
    background: var(--bg);
    color: var(--text);
}

.form-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
}

.btn {
    display: inline-block;
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.2s;
}

.btn:hover { opacity: 0.9; }
.btn-primary { background: var(--primary); color: white; }

.save-status {
    display: inline-block;
    margin-left: 10px;
    font-size: 13px;
    color: var(--success);
}

/* ── Desktop responsive: wider + side-by-side ── */
@media (min-width: 768px) {
    .stat-value { font-size: 22px; }
    .quick-stats { gap: 12px; }
    .chart-wrap { height: 250px; }
}

@media (min-width: 1024px) {
    main {
        max-width: 1100px;
        padding: 20px 24px;
    }

    .dashboard-grid {
        display: grid;
        grid-template-columns: 380px 1fr;
        gap: 20px;
        align-items: start;
    }

    /* On desktop, charts panel is open by default (JS handles this) */
    .charts-panel .details-content {
        padding-top: 4px;
    }

    .chart-wrap {
        height: 280px;
    }

    .cylinder {
        width: 160px;
    }

    .cylinder-body {
        height: 240px;
    }

    .cylinder-cap {
        height: 32px;
    }

    .cylinder-cap-top {
        margin-bottom: -16px;
    }

    .cylinder-cap-bottom {
        margin-top: -16px;
    }

    .tank-percent {
        font-size: 48px;
    }
}