/* The TCP simulator. Opened full screen or in an iframe, which cannot see the
   site's own light/dim switch, so it follows the reader's system preference,
   as the NAT and OSPF demos do. */

:root {
  --bg: #ffffff;
  --card: #ffffff;
  --border: #dfe3e8;
  --text: #22272e;
  --dim: #5f6b78;
  --accent: #0077b8;
  --btn: #f4f5f7;
  --panel: #0d2436;
  --panel-text: #eaf1f6;
  --line: #9aa8b4;
  --a: #c96a12;
  --b: #2f62cc;
  --ok: #1f8a45;
  --warn: #b7791f;
  --bad: #d23b3b;
  --acker: #8e44c9;
  --flash: rgba(255, 196, 0, 0.3);
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1d2b;
    --card: #112b40;
    --border: #234862;
    --text: #eaf1f6;
    --dim: #9fb2c2;
    --accent: #4fb3ff;
    --btn: #16374f;
    --panel: #081b29;
    --panel-text: #eaf1f6;
    --line: #5b7382;
    --a: #f0a050;
    --b: #7ea6ff;
    --ok: #5fd38a;
    --warn: #f2c14e;
    --bad: #ff6b6b;
    --acker: #c79bff;
    --flash: rgba(255, 196, 0, 0.18);
  }
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}
code { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.tcp-app { padding: 0.5rem 16px 1.5rem; max-width: 1500px; margin: 0 auto; }
.tcp-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 0.2rem 0.9rem; margin: 0 0 0.45rem; }
.tcp-head h1 { font-size: 1.3rem; margin: 0; letter-spacing: -0.01em; }
.tcp-head p { margin: 0; color: var(--dim); font-size: 0.92rem; }
.in-viewer .tcp-head { display: none; } /* the viewer page's top bar holds it */

/* --- controls */
.tcp-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 0.5rem 0.75rem; }
.tcp-btn {
  background: var(--btn); color: var(--text); border: 1px solid var(--border);
  border-radius: 8px; padding: 0.35rem 0.9rem; font-size: 0.88rem; cursor: pointer;
}
.tcp-btn:hover:not(:disabled) { border-color: var(--accent); }
.tcp-btn:disabled { opacity: 0.45; cursor: default; }
.tcp-btn.play { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; min-width: 6rem; }
.tcp-btn.go { border-color: var(--accent); color: var(--accent); font-weight: 600; }
.tcp-btn.bad { border-color: var(--bad); color: var(--bad); }
.tcp-btn.small { padding: 0.18rem 0.6rem; font-size: 0.8rem; border-radius: 6px; }
.tcp-btn.tiny { padding: 0.05rem 0.45rem; font-size: 0.74rem; border-radius: 5px; }
.tcp-check { display: inline-flex; align-items: center; gap: 0.35rem; font-size: 0.86rem; }
.tcp-check input { accent-color: var(--accent); }
.tcp-app select {
  background: var(--btn); color: var(--text); border: 1px solid var(--border); border-radius: 7px;
  padding: 0.3rem 0.4rem; font-size: 0.86rem;
}

/* --- what the current event did */
.tcp-say {
  display: flex; gap: 0.9rem; align-items: baseline; margin: 0.5rem 0;
  background: var(--panel); color: var(--panel-text); border-radius: 8px; padding: 0.45rem 0.9rem;
  border-left: 5px solid var(--accent);
  /* A fixed height, so a longer event does not move the buttons under the pointer. */
  height: 5rem; overflow-y: auto;
}
.tcp-say.ok { border-left-color: var(--ok); }
.tcp-say.warn { border-left-color: var(--warn); }
.tcp-say.bad { border-left-color: var(--bad); }
.tcp-say .n { font-family: ui-monospace, Menlo, monospace; font-size: 0.78rem; opacity: 0.7; white-space: nowrap; }
.tcp-say p { margin: 0; }
.tcp-say .main { font-size: 1.05rem; font-weight: 600; line-height: 1.3; margin-bottom: 0.15rem; }
.tcp-say .more { font-size: 0.88rem; line-height: 1.4; opacity: 0.92; }

/* --- three columns: host, ladder, host */
.tcp-main { display: grid; gap: 0.75rem; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); grid-template-areas: 'a b' 'c c'; }
#host-0 { grid-area: a; }
#host-1 { grid-area: b; }
.tcp-center { grid-area: c; min-width: 0; display: flex; flex-direction: column; gap: 0.6rem; }
@media (min-width: 1150px) {
  .tcp-main { grid-template-columns: 300px minmax(0, 1fr) 300px; grid-template-areas: 'a c b'; }
}
@media (max-width: 640px) {
  .tcp-main { grid-template-columns: minmax(0, 1fr); grid-template-areas: 'a' 'b' 'c'; }
}

.tcp-box, .tcp-host { border: 1px solid var(--border); border-radius: 12px; background: var(--card); padding: 0.65rem 0.8rem; font-size: 0.84rem; min-width: 0; }
.tcp-box h2, .tcp-host h2 { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.04em; color: var(--dim); margin: 0 0 0.45rem; }
.tcp-box h2 .sub { text-transform: none; letter-spacing: 0; font-weight: 400; margin-left: 0.4rem; }
.empty { color: var(--dim); margin: 0.2rem 0; }

/* --- a host */
.tcp-host { border-top: 4px solid var(--c); }
.d0 { --c: var(--a); }
.d1 { --c: var(--b); }
.tcp-host h2 { display: flex; align-items: center; gap: 0.4rem; text-transform: none; letter-spacing: 0; font-size: 1rem; color: var(--text); }
.tcp-host h2 code { font-size: 0.8rem; color: var(--dim); font-weight: 400; }
.tcp-host h2 .dot { width: 0.7rem; height: 0.7rem; border-radius: 50%; background: var(--c); }
.tcp-host .st { display: flex; flex-wrap: wrap; align-items: center; gap: 0.4rem; margin-bottom: 0.45rem; }
.badge { font-family: ui-monospace, Menlo, Consolas, monospace; font-weight: 700; font-size: 0.95rem; padding: 0.15rem 0.55rem; border-radius: 6px; background: var(--btn); border: 1px solid var(--border); }
.badge.s-ESTABLISHED { background: color-mix(in srgb, var(--ok) 18%, var(--card)); border-color: var(--ok); }
.badge.s-LISTEN { border-color: var(--accent); }
.owes { font-size: 0.78rem; color: var(--warn); font-weight: 600; }
.calls { display: flex; flex-direction: column; gap: 0.3rem; margin-bottom: 0.6rem; }
.act {
  display: flex; flex-direction: column; align-items: flex-start; gap: 0.05rem; text-align: left;
  background: var(--btn); color: var(--text); border: 1px solid var(--border); border-left: 4px solid var(--c);
  border-radius: 8px; padding: 0.3rem 0.6rem; cursor: pointer; font: inherit;
}
.act b { font-size: 0.86rem; font-weight: 600; }
.act small { font-size: 0.72rem; color: var(--dim); font-family: ui-monospace, Menlo, Consolas, monospace; overflow-wrap: anywhere; }
.act:hover:not(:disabled) { border-color: var(--c); background: color-mix(in srgb, var(--c) 10%, var(--btn)); }
.act:disabled { opacity: 0.45; cursor: default; border-left-color: var(--border); }
.act:disabled small { font-family: inherit; }
.vars { width: 100%; border-collapse: collapse; font-size: 0.8rem; margin-bottom: 0.2rem; border-top: 1px solid var(--border); }
.vars th { text-align: left; font-weight: 600; color: var(--dim); font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.04em; border-bottom: 1px solid var(--border); padding: 0.1rem 0.2rem; }
.vars td { padding: 0.1rem 0.15rem; font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 0.74rem; }
.vars td:nth-child(odd) { color: var(--dim); font-family: inherit; font-size: 0.68rem; cursor: help; white-space: nowrap; }
.vars .na { color: var(--dim); }

.dlen { display: flex; align-items: center; gap: 0.35rem; margin: -0.1rem 0 0.1rem 0.9rem; font-size: 0.76rem; color: var(--dim); font-family: ui-monospace, Menlo, Consolas, monospace; }
.dlen input {
  width: 4.2rem; background: var(--btn); color: var(--text); border: 1px solid var(--border); border-radius: 6px;
  padding: 0.15rem 0.35rem; font-size: 0.82rem; font-family: inherit;
}
.dlen.off { opacity: 0.45; }

/* --- the ladder */
.tcp-names { display: flex; justify-content: space-between; font-weight: 700; font-size: 0.9rem; padding: 0 calc(17% - 2rem); }
.tcp-names .d0 { color: var(--a); }
.tcp-names .d1 { color: var(--b); }
.tcp-ladder { border: 1px solid var(--border); border-radius: 12px; background: var(--card); max-height: 620px; min-height: 260px; overflow: auto; }
#tcp-svg { display: block; width: 100%; min-width: 640px; user-select: none; }
.t-line { stroke: var(--line); stroke-width: 3; stroke-linecap: round; }
.t-state { font-size: 11px; font-weight: 700; fill: var(--text); font-family: ui-monospace, Menlo, Consolas, monospace; }
.t-call { fill: var(--accent); }
.t-calltxt { font-size: 11px; fill: var(--accent); font-family: ui-monospace, Menlo, Consolas, monospace; }
.t-now { stroke: var(--accent); stroke-width: 1.5; stroke-dasharray: 5 4; }
.t-nowtxt { font-size: 11px; fill: var(--accent); font-weight: 700; }
.future { opacity: 0.22; }

.pk { stroke-width: 2.2; }
.pk.d0 { stroke: var(--a); }
.pk.d1 { stroke: var(--b); }
.pk.flight { stroke-dasharray: 6 5; }
.pk.focus { stroke-width: 4.5; }
.pk-id { font-size: 10.5px; font-weight: 800; font-family: ui-monospace, Menlo, Consolas, monospace; paint-order: stroke; stroke: var(--card); stroke-width: 3px; }
.pk-id.d0 { fill: var(--a); }
.pk-id.d1 { fill: var(--b); }
.pk-x { stroke: var(--bad); stroke-width: 3.5; stroke-linecap: round; }
.pk-v { stroke: var(--card); stroke-width: 2; }
.pk-v.ok { fill: var(--ok); }
.pk-v.warn { fill: var(--warn); }
.pk-v.bad { fill: var(--bad); }
.pk-link { fill: none; stroke-width: 2; stroke-dasharray: 3 3; }
.pk-link.acked { stroke: var(--ok); }
.pk-link.acker { stroke: var(--acker); }
.pk-link.retx { stroke: var(--warn); }

.card { cursor: pointer; }
.card .bg { fill: var(--card); stroke: var(--border); stroke-width: 1.3; }
.card.d0 .edge { fill: var(--a); }
.card.d1 .edge { fill: var(--b); }
.card text { font-size: 11px; font-family: ui-monospace, Menlo, Consolas, monospace; fill: var(--text); }
.card .id { font-weight: 800; }
.card .fl { font-weight: 700; }
.card .fl.SYN { fill: #8e44c9; }
.card .fl.ACK { fill: var(--ok); }
.card .fl.FIN { fill: var(--warn); }
.card .fl.RST { fill: var(--bad); }
.card .fl.PSH, .card .fl.none { fill: var(--dim); }
.card .nums .k { fill: var(--dim); }
.card .nums .off { fill: var(--dim); }
.card .tag { font-size: 10px; font-family: -apple-system, 'Segoe UI', Roboto, sans-serif; font-weight: 600; }
.card .tag .ok { fill: var(--ok); }
.card .tag .warn { fill: var(--warn); }
.card .tag .retx { fill: var(--warn); }
.card.lost .bg { stroke: var(--bad); }
.card.hov .bg { stroke: var(--accent); }
.card.sel .bg { stroke: var(--accent); stroke-width: 2.5; stroke-dasharray: none; fill: color-mix(in srgb, var(--flash) 60%, var(--card)); }
.card.acked .bg { stroke: var(--ok); stroke-width: 2.5; stroke-dasharray: none; }
.card.acker .bg { stroke: var(--acker); stroke-width: 2.5; stroke-dasharray: none; }
.card.retx .bg { stroke: var(--warn); stroke-width: 2.5; stroke-dasharray: none; }
.card.future { opacity: 0.3; }

/* --- the controls on a segment in flight */
.pk-btn { cursor: pointer; }
.pk-btn rect { fill: var(--card); stroke-width: 1.4; }
.pk-btn text { font-size: 10.5px; font-weight: 700; font-family: -apple-system, 'Segoe UI', Roboto, sans-serif; }
.pk-btn.deliver rect { stroke: var(--accent); }
.pk-btn.deliver text { fill: var(--accent); }
.pk-btn.drop rect { stroke: var(--bad); }
.pk-btn.drop text { fill: var(--bad); }
.pk-btn:hover rect { fill: color-mix(in srgb, var(--flash) 60%, var(--card)); }

/* --- every segment so far, and what became of it */
.tcp-flight { max-height: 220px; overflow-y: auto; }
.fl-item { display: flex; flex-wrap: wrap; align-items: baseline; gap: 0.2rem 0.6rem; padding: 0.25rem 0 0.25rem 0.5rem; border-left: 4px solid var(--c); margin-bottom: 0.25rem; cursor: pointer; }
.fl-item:hover, .fl-item.sel { background: color-mix(in srgb, var(--flash) 45%, transparent); }
.fl-item .what { flex: 1 1 16rem; }
.fl-item .flg { font-weight: 700; font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 0.8rem; }
.fl-item code { font-size: 0.78rem; color: var(--dim); }
.fate { font-size: 0.78rem; }
.fate.wire { color: var(--accent); font-weight: 600; }
.fate.ok { color: var(--ok); }
.fate.warn { color: var(--warn); }
.fate.bad { color: var(--bad); }

/* --- the selected segment */
.tcp-detail { margin-top: 0.75rem; }
.tcp-detail h2 { display: flex; align-items: center; }
.tcp-detail .x { margin-left: auto; border: 0; background: none; color: var(--dim); font-size: 1.2rem; cursor: pointer; }
.det { display: grid; gap: 0.9rem; grid-template-columns: minmax(0, 1fr); }
@media (min-width: 900px) { .det { grid-template-columns: minmax(0, 560px) minmax(0, 1fr); } }
.hdr { display: grid; grid-template-columns: repeat(32, minmax(0, 1fr)); border: 1px solid var(--border); border-radius: 6px; overflow: hidden; }
.hdr .f { border: 1px solid var(--border); margin: -1px 0 0 -1px; padding: 0.2rem 0.35rem; display: flex; flex-direction: column; min-width: 0; overflow: hidden; }
.hdr .f b { font-size: 0.66rem; font-weight: 600; color: var(--dim); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.hdr .f span { font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 0.86rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.hdr .f small { font-family: -apple-system, 'Segoe UI', Roboto, sans-serif; font-size: 0.72rem; color: var(--dim); }
.hdr .f.hi { background: color-mix(in srgb, var(--flash) 45%, transparent); }
.hdr .f.bit { padding: 0.2rem 0; text-align: center; align-items: center; }
.hdr .f.bit.set { background: var(--accent); }
.hdr .f.bit.set b, .hdr .f.bit.set span { color: #fff; }
.hdr .f.data span { white-space: normal; }
.hdr .f.data code { font-size: 0.8rem; }
.facts { margin: 0; padding-left: 1.1rem; line-height: 1.45; }
.facts li { margin-bottom: 0.25rem; }
.facts li.ok { color: var(--ok); }
.facts li.warn { color: var(--warn); }
.facts li.bad { color: var(--bad); }
.facts li.retx { color: var(--warn); }
.facts a { color: var(--accent); cursor: pointer; text-decoration: underline; font-weight: 700; }
.acts { display: flex; gap: 0.4rem; margin-top: 0.4rem; }

/* --- the legend under the simulator */
.tcp-legend { margin-top: 0.75rem; }
.tcp-legend .lead { margin: 0 0 0.6rem; font-size: 0.9rem; line-height: 1.45; }
.tcp-legend ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.45rem 1.4rem; grid-template-columns: minmax(0, 1fr); }
@media (min-width: 900px) { .tcp-legend ul { grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); } }
.tcp-legend li { display: flex; gap: 0.7rem; align-items: flex-start; line-height: 1.4; }
.tcp-legend svg { flex: none; width: 60px; height: 24px; overflow: visible; }
.leg-card { fill: var(--card); stroke: var(--border); stroke-width: 1.2; }
.leg-t { font-size: 8.5px; font-weight: 700; font-family: ui-monospace, Menlo, Consolas, monospace; fill: var(--text); }
.tcp-legend .t-state { font-size: 9px; }