/* ── Reset & base ────────────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
    --bg:        #0a0f1e;
    --surface:   #0f172a;
    --surface2:  #1e293b;
    --border:    #1e293b;
    --text:      #f1f5f9;
    --muted:     #64748b;
    --accent:    #f43f5e;
    --accent2:   #fb7185;
    --green:     #22c55e;
    --amber:     #f59e0b;
    --blue:      #3b82f6;
    --purple:    #a855f7;
    --radius:    14px;

    /* Zone colours */
    --zone-rest:   #3b82f6;
    --zone-fat:    #22c55e;
    --zone-cardio: #f59e0b;
    --zone-peak:   #f43f5e;
}

html, body {
    height: 100%;
    font-family: "Inter", system-ui, sans-serif;
    background: var(--bg);
    color: var(--text);
    overflow-x: hidden;
}

/* ── Connect overlay ─────────────────────────────────────────────────────── */
.overlay {
    position: fixed; inset: 0;
    display: flex; align-items: center; justify-content: center;
    background: radial-gradient(ellipse at 50% 0%, #1e1040 0%, var(--bg) 70%);
    z-index: 100;
    transition: opacity .3s, visibility .3s;
}
.overlay.hidden { opacity: 0; visibility: hidden; pointer-events: none; }

.glass {
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid rgba(255,255,255,.08);
    border-radius: 24px;
    box-shadow: 0 24px 64px rgba(0,0,0,.6), 0 0 0 1px rgba(255,255,255,.04);
}

.modal {
    width: min(440px, 92vw);
    padding: 40px 36px;
    display: flex; flex-direction: column; gap: 22px;
    align-items: center; text-align: center;
}

.modal-icon {
    width: 64px; height: 64px;
    border-radius: 18px;
    background: linear-gradient(135deg, rgba(244,63,94,.25), rgba(244,63,94,.08));
    border: 1px solid rgba(244,63,94,.3);
    display: flex; align-items: center; justify-content: center;
    color: var(--accent);
}
.modal-icon svg { width: 30px; height: 30px; }

.modal-title {
    font-size: 1.75rem; font-weight: 700;
    background: linear-gradient(135deg, #fff 30%, #94a3b8);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text;
}
.modal-sub { color: var(--muted); font-size: .95rem; margin-top: -16px; }

.form-row { width: 100%; text-align: left; display: flex; flex-direction: column; gap: 8px; }
.form-row label {
    font-size: .85rem; font-weight: 500; color: var(--muted);
    display: flex; justify-content: space-between; align-items: center;
}
.form-row label a { color: var(--accent2); font-size: .8rem; text-decoration: none; }
.form-row label a:hover { text-decoration: underline; }
.form-row input {
    width: 100%; padding: 12px 16px;
    background: rgba(255,255,255,.05);
    border: 1px solid rgba(255,255,255,.1);
    border-radius: 10px;
    color: var(--text);
    font-family: "JetBrains Mono", monospace;
    font-size: .9rem;
    outline: none;
    transition: border-color .2s;
}
.form-row input:focus { border-color: var(--accent); }
.form-row input::placeholder { color: var(--muted); }

/* ── Buttons ─────────────────────────────────────────────────────────────── */
.btn-primary {
    width: 100%; padding: 14px 20px;
    background: linear-gradient(135deg, #f43f5e, #e11d48);
    border: none; border-radius: 12px;
    color: #fff; font-size: 1rem; font-weight: 600;
    cursor: pointer; transition: opacity .2s, transform .15s;
    display: flex; align-items: center; justify-content: center; gap: 10px;
    box-shadow: 0 8px 24px rgba(244,63,94,.35);
}
.btn-primary:hover:not(:disabled) { opacity: .90; transform: translateY(-1px); }
.btn-primary:active:not(:disabled){ transform: translateY(0); }
.btn-primary:disabled { opacity: .4; cursor: not-allowed; }
.btn-icon svg { width: 18px; height: 18px; }

.btn-ghost {
    padding: 7px 14px;
    background: transparent;
    border: 1px solid rgba(255,255,255,.12);
    border-radius: 8px;
    color: var(--muted); font-size: .85rem;
    cursor: pointer; transition: color .2s, border-color .2s;
}
.btn-ghost:hover { color: var(--text); border-color: rgba(255,255,255,.25); }
.btn-sm { padding: 5px 11px; font-size: .78rem; }

/* ── Status msg ──────────────────────────────────────────────────────────── */
.status-msg {
    min-height: 22px; font-size: .85rem;
    color: var(--muted); text-align: center;
    transition: all .2s;
}
.status-msg.info  { color: var(--blue); }
.status-msg.warn  { color: var(--amber); }
.status-msg.error { color: var(--accent); }

/* ── App layout ──────────────────────────────────────────────────────────── */
.app {
    display: grid;
    grid-template-rows: auto 1fr auto;
    min-height: 100vh;
    grid-template-areas: "topbar" "hero" "chart";
}
.app.hidden { display: none; }

/* ── Topbar ──────────────────────────────────────────────────────────────── */
.topbar {
    grid-area: topbar;
    display: flex; align-items: center; gap: 16px;
    padding: 14px 28px;
    background: rgba(15,23,42,.8);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    position: sticky; top: 0; z-index: 10;
}
.topbar-brand {
    display: flex; align-items: center; gap: 9px;
    font-weight: 700; font-size: 1.05rem;
}
.brand-icon { width: 22px; height: 22px; color: var(--accent); }

.topbar-stats { display: flex; align-items: center; gap: 10px; margin-left: auto; }
.stat-pill {
    display: flex; align-items: center; gap: 6px;
    padding: 5px 12px;
    background: var(--surface2);
    border-radius: 100px;
    font-size: .8rem; color: var(--muted);
}
.stat-pill svg { width: 14px; height: 14px; }
.stat-pill span { color: var(--text); font-weight: 600; }

.connection-dot {
    width: 10px; height: 10px; border-radius: 50%;
    background: var(--muted);
    transition: background .3s, box-shadow .3s;
}
.connection-dot.online {
    background: var(--green);
    box-shadow: 0 0 8px var(--green);
    animation: pulse-dot 2s ease-in-out infinite;
}
@keyframes pulse-dot {
    0%, 100% { box-shadow: 0 0 6px var(--green); }
    50%       { box-shadow: 0 0 14px var(--green); }
}

/* ── Hero ────────────────────────────────────────────────────────────────── */
.hero {
    grid-area: hero;
    display: flex; flex-direction: column; align-items: center;
    justify-content: center; gap: 32px;
    padding: 48px 24px 40px;
    background: radial-gradient(ellipse 80% 60% at 50% -10%, rgba(244,63,94,.12) 0%, transparent 70%);
}

.hr-display { text-align: center; }

.hr-label {
    font-size: .72rem; letter-spacing: .18em; font-weight: 600;
    color: var(--muted); margin-bottom: 8px;
}

.hr-value-wrap {
    display: flex; align-items: baseline; justify-content: center; gap: 10px;
}
.hr-value {
    font-size: clamp(5rem, 18vw, 9rem);
    font-weight: 700; line-height: 1;
    font-variant-numeric: tabular-nums;
    background: linear-gradient(135deg, #fff 40%, #f43f5e);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text;
    transition: transform .1s;
}
.hr-value.pulse { animation: hr-pulse .5s ease-out; }
@keyframes hr-pulse {
    0%  { transform: scale(1); }
    40% { transform: scale(1.055); }
    100%{ transform: scale(1); }
}
.hr-unit {
    font-size: 1.4rem; font-weight: 500; color: var(--muted);
    align-self: flex-end; padding-bottom: 10px;
}
.hr-ts { font-size: .8rem; color: var(--muted); margin-top: 6px; }

/* Heart rate zones */
.hr-zones {
    display: flex; gap: 10px; margin-top: 24px;
    justify-content: center; flex-wrap: wrap;
}
.zone {
    padding: 8px 16px; border-radius: 10px;
    font-size: .7rem; font-weight: 600; text-align: center;
    color: var(--muted);
    border: 1px solid var(--border);
    opacity: .5;
    transition: opacity .3s, color .3s, border-color .3s, box-shadow .3s;
    line-height: 1.5;
}
.zone span { font-weight: 400; display: block; }
.zone[data-zone="rest"].active   { color: var(--zone-rest);   border-color: var(--zone-rest);   box-shadow: 0 0 16px rgba(59,130,246,.3); opacity:1; }
.zone[data-zone="fat"].active    { color: var(--zone-fat);    border-color: var(--zone-fat);    box-shadow: 0 0 16px rgba(34,197,94,.3);  opacity:1; }
.zone[data-zone="cardio"].active { color: var(--zone-cardio); border-color: var(--zone-cardio); box-shadow: 0 0 16px rgba(245,158,11,.3); opacity:1; }
.zone[data-zone="peak"].active   { color: var(--zone-peak);   border-color: var(--zone-peak);   box-shadow: 0 0 16px rgba(244,63,94,.3);  opacity:1; }

/* Session stats */
.session-stats {
    display: flex; gap: 20px; flex-wrap: wrap; justify-content: center;
}
.sstat {
    min-width: 72px; text-align: center;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px; padding: 14px 18px;
}
.sstat-val { font-size: 1.6rem; font-weight: 700; font-variant-numeric: tabular-nums; }
.sstat-lbl { font-size: .65rem; letter-spacing: .12em; color: var(--muted); font-weight: 600; margin-top: 2px; }

/* ── Chart section ───────────────────────────────────────────────────────── */
.chart-section {
    grid-area: chart;
    padding: 0 20px 28px;
}
.chart-header {
    display: flex; align-items: center; justify-content: space-between;
    margin-bottom: 10px;
}
.chart-title { font-weight: 600; font-size: .95rem; }
.chart-sub   { color: var(--muted); font-size: .8rem; font-weight: 400; }
.chart-container { height: 220px; border-radius: var(--radius); overflow: hidden; }

/* ── Scrollbar ───────────────────────────────────────────────────────────── */
::-webkit-scrollbar          { width: 6px; }
::-webkit-scrollbar-track    { background: var(--bg); }
::-webkit-scrollbar-thumb    { background: var(--surface2); border-radius: 3px; }