/* ═══════════════════════════════════════════════════════════════
   PoolChem — The Swimming Pool Chemical Dose Calculator
   Bespoke theme: Pool water blue on clean white (light default)
   Deliberate light-mode default — used poolside in bright sun
   ═══════════════════════════════════════════════════════════════ */

:root {
    --bg-primary: #f0f9ff;
    --bg-surface: #ffffff;
    --bg-hover: #e0f2fe;
    --bg-input: #f0f9ff;
    --text-primary: #0c4a6e;
    --text-secondary: #1e6b8a;
    --text-muted: #5e8090;
    --accent: #0ea5e9;
    --accent-hover: #0284c7;
    --accent-glow: rgba(14, 165, 233, 0.1);
    --accent-glow-strong: rgba(14, 165, 233, 0.2);
    --border: rgba(12, 74, 110, 0.1);
    --border-hover: rgba(14, 165, 233, 0.4);
    --success: #16a34a;
    --success-bg: rgba(22, 163, 74, 0.08);
    --warning: #d97706;
    --warning-bg: rgba(217, 119, 6, 0.08);
    --error: #dc2626;
    --error-bg: rgba(220, 38, 38, 0.08);
    --radius: 12px;
    --radius-sm: 8px;
    --shadow: 0 1px 8px rgba(0, 0, 0, 0.06);
    --transition: 0.2s ease;
}

[data-theme="dark"] {
    --bg-primary: #0a1520;
    --bg-surface: #0e1e2c;
    --bg-hover: #162a3c;
    --bg-input: #0c1a28;
    --text-primary: #e0f2fe;
    --text-secondary: #7dd3fc;
    --text-muted: #4a8aaa;
    --border: rgba(125, 211, 252, 0.1);
    --shadow: 0 2px 12px rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-secondary);
    line-height: 1.6;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
}

.container { max-width: 1100px; margin: 0 auto; padding: 0 1rem; }

.site-header {
    background: linear-gradient(135deg, #0284c7 0%, #0ea5e9 50%, #38bdf8 100%);
    border-bottom: 1px solid var(--border);
    padding: 2rem 0 1.5rem;
    text-align: center;
}
.header-inner { display: flex; flex-direction: column; align-items: center; gap: 0.25rem; }
.brand { display: flex; align-items: center; gap: 0.75rem; }
.brand-icon { font-size: 2rem; }
.brand-name { font-family: 'Outfit', sans-serif; font-weight: 800; font-size: clamp(1.8rem, 5vw, 2.5rem); color: #ffffff; letter-spacing: -0.02em; }
.brand-tagline { font-family: 'Outfit', sans-serif; font-weight: 600; font-size: 1rem; color: rgba(255,255,255,0.9); margin-top: 0.25rem; }
.brand-subtitle { font-size: 0.9rem; color: rgba(255,255,255,0.75); max-width: 520px; margin-top: 0.25rem; }

.privacy-badge { display: inline-flex; align-items: center; gap: 0.5rem; background: var(--accent-glow); border: 1px solid rgba(14, 165, 233, 0.2); border-radius: 999px; padding: 0.4rem 1rem; font-size: 0.8rem; font-weight: 500; color: var(--accent); margin: 1.5rem auto 1rem; text-align: center; width: fit-content; }

.app-grid { display: grid; grid-template-columns: 1fr; gap: 1.5rem; margin-top: 1rem; }
@media (min-width: 768px) { .app-grid { grid-template-columns: 420px 1fr; } }

.panel { background: var(--bg-surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.5rem; box-shadow: var(--shadow); }
.panel-title { font-family: 'Outfit', sans-serif; font-weight: 700; font-size: 1.35rem; color: var(--text-primary); margin-bottom: 1.25rem; }

.input-group { margin-bottom: 1.25rem; }
.input-group--half { flex: 1; min-width: 0; }
.input-group--third { flex: 1; min-width: 0; }
.input-row { display: flex; gap: 1rem; margin-bottom: 1.25rem; }

label { display: block; font-size: 0.85rem; font-weight: 600; color: var(--text-primary); margin-bottom: 0.4rem; }

input[type="number"], select {
    width: 100%; padding: 0.65rem 0.85rem; background: var(--bg-input); border: 1px solid var(--border); border-radius: var(--radius-sm); color: var(--text-primary); font-family: 'JetBrains Mono', monospace; font-size: 0.95rem; transition: border-color var(--transition), box-shadow var(--transition); appearance: none;
}
select { font-family: 'Inter', sans-serif; font-size: 0.85rem; cursor: pointer; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%235e8090' d='M6 8L1 3h10z'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right 0.75rem center; padding-right: 2rem; }
input:focus, select:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-glow); }
.input-hint { display: block; font-size: 0.75rem; color: var(--text-muted); margin-top: 0.3rem; }

/* ── Volume Calculator Accordion ── */
.volume-calculator { margin-bottom: 1.25rem; border: 1px solid var(--border); border-radius: var(--radius-sm); }
.vol-calc-toggle { padding: 0.75rem 1rem; font-size: 0.85rem; font-weight: 600; color: var(--accent); cursor: pointer; list-style: none; }
.vol-calc-toggle::-webkit-details-marker { display: none; }
.vol-calc-body { padding: 0 1rem 1rem; }
.btn-vol-calc { padding: 0.5rem 1.2rem; font-size: 0.82rem; font-weight: 600; background: var(--accent-glow-strong); border: 1px solid var(--accent); border-radius: var(--radius-sm); color: var(--accent); cursor: pointer; transition: all var(--transition); }
.btn-vol-calc:hover { background: var(--accent); color: #fff; }

/* ── Chemistry Input Grid ── */
.section-subtitle { font-family: 'Outfit', sans-serif; font-weight: 700; font-size: 1.1rem; color: var(--text-primary); margin-bottom: 0.5rem; }
.section-hint { font-size: 0.82rem; color: var(--text-muted); margin-bottom: 1rem; }

.chem-input-grid { display: grid; grid-template-columns: 1fr; gap: 0.75rem; margin-bottom: 1.25rem; }
@media (min-width: 480px) { .chem-input-grid { grid-template-columns: 1fr 1fr; } }

.chem-input { background: var(--bg-hover); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 0.75rem; }
.chem-input label { margin-bottom: 0.3rem; font-size: 0.78rem; }
.chem-input input { font-size: 0.9rem; padding: 0.5rem 0.7rem; }
.chem-range { display: block; font-size: 0.7rem; color: var(--text-muted); margin-top: 0.2rem; font-family: 'JetBrains Mono', monospace; }

/* ── Button ── */
.btn-calculate { width: 100%; padding: 0.85rem; font-size: 1rem; font-weight: 700; background: linear-gradient(135deg, var(--accent), var(--accent-hover)); border: none; border-radius: var(--radius-sm); color: #ffffff; cursor: pointer; transition: all var(--transition); font-family: 'Inter', sans-serif; margin-top: 0.5rem; }
.btn-calculate:hover { transform: translateY(-1px); box-shadow: 0 4px 16px rgba(14, 165, 233, 0.3); }

.error-message { background: var(--error-bg); border: 1px solid rgba(220, 38, 38, 0.3); border-radius: var(--radius-sm); padding: 0.75rem 1rem; font-size: 0.85rem; color: var(--error); margin-bottom: 1rem; }
.hidden { display: none !important; }

/* ── Parameter Cards ── */
.param-grid { display: grid; grid-template-columns: 1fr; gap: 0.75rem; margin-bottom: 1.25rem; }

.param-card { background: var(--bg-hover); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 1rem; transition: border-color var(--transition); }
.param-card:hover { border-color: var(--border-hover); }

.param-card--ok { border-left: 3px solid var(--success); }
.param-card--low { border-left: 3px solid var(--warning); }
.param-card--high { border-left: 3px solid var(--error); }

.param-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 0.5rem; }
.param-name { font-weight: 600; font-size: 0.85rem; color: var(--text-primary); }
.param-badge { font-size: 0.72rem; font-weight: 700; padding: 0.2rem 0.6rem; border-radius: 999px; text-transform: uppercase; letter-spacing: 0.04em; }
.param-badge--ok { background: var(--success-bg); color: var(--success); }
.param-badge--low { background: var(--warning-bg); color: var(--warning); }
.param-badge--high { background: var(--error-bg); color: var(--error); }

.param-dose { font-family: 'JetBrains Mono', monospace; font-size: 0.88rem; color: var(--text-secondary); }

/* ── Priority Order ── */
.priority-order { margin-bottom: 1.25rem; }
.priority-list { padding-left: 1.25rem; }
.priority-list li { padding: 0.4rem 0; font-size: 0.85rem; color: var(--text-secondary); border-bottom: 1px solid var(--border); }
.priority-list li:last-child { border-bottom: none; }
.priority-list strong { color: var(--text-primary); }

/* ── Export ── */
.export-row { display: flex; gap: 0.75rem; margin-bottom: 1.25rem; }
.btn-export { display: inline-flex; align-items: center; gap: 0.4rem; padding: 0.5rem 1rem; font-size: 0.8rem; font-weight: 600; background: var(--bg-hover); border: 1px solid var(--border); border-radius: var(--radius-sm); color: var(--text-secondary); cursor: pointer; transition: all var(--transition); }
.btn-export:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-glow); }

/* ── How It Works ── */
.how-it-works { margin-top: 2.5rem; padding: 2rem 0; }
.how-title { text-align: center; margin-bottom: 1.5rem; }
.how-grid { display: grid; grid-template-columns: 1fr; gap: 1rem; }
@media (min-width: 600px) { .how-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 900px) { .how-grid { grid-template-columns: repeat(4, 1fr); } }
.how-card { background: var(--bg-surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.25rem; text-align: center; transition: border-color var(--transition), transform var(--transition); }
.how-card:hover { border-color: var(--border-hover); transform: translateY(-2px); }
.how-icon { font-size: 1.8rem; display: block; margin-bottom: 0.75rem; }
.how-card-title { font-family: 'Outfit', sans-serif; font-weight: 700; font-size: 1rem; color: var(--text-primary); margin-bottom: 0.5rem; }
.how-card p { font-size: 0.82rem; color: var(--text-muted); line-height: 1.5; }

.seo-card { background: var(--bg-surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.5rem; margin-top: 1.5rem; }
.seo-card h2 { font-family: 'Outfit', sans-serif; font-weight: 700; font-size: 1.25rem; color: var(--text-primary); margin-bottom: 0.75rem; }
.seo-card p { font-size: 0.9rem; color: var(--text-secondary); line-height: 1.7; }
.seo-card strong { color: var(--text-primary); }

.site-footer { text-align: center; padding: 2rem 0; margin-top: 2rem; border-top: 1px solid var(--border); }
.footer-privacy { font-size: 0.82rem; font-weight: 500; color: var(--accent); margin-bottom: 0.4rem; }
.footer-disclaimer, .footer-copyright { font-size: 0.75rem; color: var(--text-muted); margin-bottom: 0.4rem; }
.footer-copyright strong { color: var(--text-secondary); }

.toast { position: fixed; bottom: 2rem; left: 50%; transform: translateX(-50%) translateY(100px); background: var(--bg-surface); border: 1px solid var(--accent); border-radius: var(--radius-sm); padding: 0.7rem 1.4rem; font-size: 0.85rem; font-weight: 500; color: var(--accent); box-shadow: 0 8px 32px rgba(0,0,0,0.15); opacity: 0; transition: all 0.3s ease; z-index: 1000; pointer-events: none; }
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

@media (max-width: 480px) { .input-row { flex-direction: column; gap: 0; } }