/* JetBrains Mono, self-hosted (OFL, see fonts/OFL.txt). The NL ("no ligatures") cut keeps
   ciphertext like -> or != as separate characters. Only the weights the styles use are loaded. */
@font-face {
  font-family: "JetBrains Mono NL";
  src: url("fonts/webfonts/JetBrainsMonoNL-Regular.woff2") format("woff2");
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "JetBrains Mono NL";
  src: url("fonts/webfonts/JetBrainsMonoNL-Medium.woff2") format("woff2");
  font-weight: 500;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "JetBrains Mono NL";
  src: url("fonts/webfonts/JetBrainsMonoNL-Bold.woff2") format("woff2");
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

/* Theme tokens. Light is the base; [data-theme="dark"] overrides it.
   data-theme is set before first paint by the inline script in index.html. */
:root {
  --bg: #e8eef1;
  --surface: #f8fafb;
  --field: #ffffff;
  --btn: #eef3f5;
  --text: #0e1b24;
  --muted: #475866;
  --line: #c3d1d7;
  --field-border: #6d838e;
  --accent: #00684d;
  --accent-2: #006577;
  --on-accent: #ffffff;
  --focus: #006577;
  --error: #b42318;
  --warning-bg: #fff3dc;
  --warning-text: #6b3d00;
  --glow: rgba(0, 104, 77, 0.14);
  --panel-shadow: 0 1px 2px rgba(14, 27, 36, 0.06), 0 8px 24px rgba(0, 101, 119, 0.08);
  --grid: rgba(0, 101, 119, 0.07);
  --haze: rgba(0, 104, 77, 0.06);
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono NL", ui-monospace, "Cascadia Mono", "SFMono-Regular", Menlo, Consolas, "Liberation Mono", monospace;
  color-scheme: light;
}

:root[data-theme="dark"] {
  --bg: #0a0e14;
  --surface: #0f1620;
  --field: #0b1119;
  --btn: #142030;
  --text: #d7e3ee;
  --muted: #93a4b8;
  --line: #1c3a3a;
  --field-border: #4a7a73;
  --accent: #00ff9c;
  --accent-2: #00e5ff;
  --on-accent: #03140c;
  --focus: #00e5ff;
  --error: #ff8095;
  --warning-bg: #2a2410;
  --warning-text: #ffd58a;
  --glow: rgba(0, 255, 156, 0.22);
  --panel-shadow: 0 0 0 1px rgba(0, 255, 156, 0.06), 0 0 28px rgba(0, 229, 255, 0.07);
  --grid: rgba(0, 229, 255, 0.045);
  --haze: rgba(0, 229, 255, 0.07);
  color-scheme: dark;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  background-color: var(--bg);
  /* Faint grid plus a soft glow at the top; panels sit on a solid surface, so text is never over the texture. */
  background-image:
    radial-gradient(ellipse 80% 50% at 50% 0%, var(--haze), transparent 70%),
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 100% 100%, 32px 32px, 32px 32px;
  font: 16px/1.5 var(--font-sans);
}

::selection { background: var(--accent); color: var(--on-accent); }

/* ---- header ---- */
.site-header {
  display: grid;
  grid-template-columns: 1fr auto;
  grid-template-areas:
    "brand menu"
    "theme theme";
  align-items: start;
  gap: 12px 16px;
  width: min(720px, 100% - 32px);
  margin: 0 auto;
  padding: 20px 0 16px;
}
.brand { grid-area: brand; min-width: 0; }
.header-theme { grid-area: theme; }
.menu { grid-area: menu; }
@media (min-width: 600px) {
  .site-header {
    grid-template-columns: 1fr auto auto;
    grid-template-areas: "brand theme menu";
  }
}

h1 {
  margin: 0;
  font: 700 1.75rem/1.2 var(--font-mono);
  letter-spacing: 0.02em;
  color: var(--accent);
}
h1 .prompt { color: var(--accent-2); margin-right: 0.35em; }
h1 .cursor { color: var(--accent-2); animation: blink 1.1s steps(1) infinite; }
@keyframes blink { 50% { opacity: 0; } }

.tagline { margin: 6px 0 0; color: var(--muted); max-width: 46ch; }

h2 { margin: 16px 0 8px; font: 700 1.2rem/1.3 var(--font-mono); color: var(--text); }

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

/* ---- theme toggle (segmented radio group) ---- */
.theme-toggle {
  display: inline-flex;
  margin: 0;
  padding: 2px;
  border: 1px solid var(--field-border);
  border-radius: 8px;
  background: var(--field);
}
.theme-toggle label { position: relative; margin: 0; font-weight: 500; }
.theme-toggle input {
  position: absolute;
  inset: 0;
  opacity: 0;
  margin: 0;
  cursor: pointer;
}
.theme-toggle span {
  display: block;
  padding: 5px 12px;
  border-radius: 6px;
  font: 0.85rem/1.4 var(--font-mono);
  color: var(--muted);
}
.theme-toggle input:checked + span { background: var(--accent); color: var(--on-accent); font-weight: 700; }
.theme-toggle input:focus-visible + span { outline: 2px solid var(--focus); outline-offset: 1px; }
.theme-toggle label:hover input:not(:checked) + span { color: var(--text); }

/* ---- main panel ---- */
main {
  width: min(720px, 100% - 32px);
  margin: 0 auto 32px;
  padding: 0 16px 20px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 12px;
  box-shadow: var(--panel-shadow);
}

.tabs { display: flex; gap: 4px; margin: 0 -16px; padding: 0 8px; border-bottom: 1px solid var(--line); }
.tabs button {
  flex: 1;
  padding: 12px 8px 10px;
  border: none;
  border-bottom: 2px solid transparent;
  border-radius: 0;
  background: transparent;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 0.9rem;
}
.tabs button:hover { color: var(--text); box-shadow: none; }
.tabs button[aria-selected="true"] { color: var(--accent); border-bottom-color: var(--accent); font-weight: 700; }

label { display: block; margin: 14px 0 4px; font-weight: 600; }
label.check { font-weight: 400; display: flex; align-items: center; gap: 8px; margin-top: 12px; }
label.check input { width: 18px; height: 18px; accent-color: var(--accent); }
#key-count { font-weight: 400; color: var(--muted); font-family: var(--font-mono); font-size: 0.85rem; }

/* ---- fields: monospace for everything typed, keys and ciphertext ---- */
input[type="text"], input[type="date"], select, textarea {
  width: 100%;
  padding: 9px 11px;
  border: 1px solid var(--field-border);
  border-radius: 6px;
  background: var(--field);
  color: var(--text);
  font: 15px/1.45 var(--font-sans);
}
input[type="text"], input[type="date"], textarea {
  font-family: var(--font-mono);
  font-size: 14px;
  /* Ciphertext is full of symbols; ligatures would merge characters like -> or != */
  font-variant-ligatures: none;
}
textarea { resize: vertical; }
textarea[readonly], input[readonly] { background: var(--bg); }
::placeholder { color: var(--muted); opacity: 1; }

/* ---- buttons ---- */
button {
  padding: 9px 16px;
  border: 1px solid var(--field-border);
  border-radius: 6px;
  background: var(--btn);
  color: var(--text);
  font: 600 15px/1.3 var(--font-sans);
  cursor: pointer;
  transition: box-shadow 0.15s ease, border-color 0.15s ease;
}
button:hover:not(:disabled) { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent), 0 0 12px var(--glow); }
button:disabled { opacity: 0.5; cursor: not-allowed; }
button.primary { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }

/* Visible keyboard focus on every interactive element */
:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }
input:focus-visible, select:focus-visible, textarea:focus-visible { outline-offset: 0; border-color: var(--focus); }

.row { display: flex; gap: 8px; margin-top: 14px; }
.row > * { flex: 1; }
.row > button:not(.primary) { flex: 0 0 auto; }

fieldset.rsa {
  margin: 16px 0 0;
  padding: 8px 14px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
}
fieldset.rsa legend { padding: 0 6px; font: 700 0.9rem var(--font-mono); color: var(--accent); }
fieldset.rsa > button { margin-top: 10px; }
.status { margin: 8px 0 0; color: var(--muted); font-family: var(--font-mono); font-size: 0.9rem; }
.warning { margin: 10px 0 8px; padding: 8px 10px; border-radius: 6px; background: var(--warning-bg); color: var(--warning-text); }
.error { color: var(--error); min-height: 1.5em; margin: 8px 0 0; }

#roman-convert { margin-top: 14px; width: 100%; }

/* Label with a small action button on the right (Result + Copy) */
.field-head { display: flex; align-items: flex-end; justify-content: space-between; gap: 8px; margin-top: 14px; }
.field-head label { margin: 0 0 4px; }
.field-head button { margin-bottom: 4px; padding: 5px 14px; font-size: 0.9rem; }
.field-actions { display: flex; gap: 6px; }

/* "Using notes.md (2.3 KB)  [Clear file]" under Input while a file is loaded */
.file-status {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin: 6px 0 0;
  color: var(--muted);
  font: 0.9rem/1.4 var(--font-mono);
  overflow-wrap: anywhere;
}
.file-status strong { color: var(--text); }
.file-status button { flex: 0 0 auto; padding: 4px 12px; font-size: 0.85rem; }

/* ---- error/info popup ---- */
dialog {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--surface);
  color: var(--text);
  box-shadow: var(--panel-shadow);
}
dialog::backdrop { background: rgba(5, 8, 12, 0.6); }
#popup { max-width: min(90vw, 480px); }
#popup p { overflow-wrap: anywhere; font-family: var(--font-mono); font-size: 0.95rem; }
#popup form { text-align: right; }
#confirm { max-width: min(90vw, 480px); }
#confirm h2 { margin-top: 4px; color: var(--accent); }
.dialog-actions { display: flex; justify-content: flex-end; gap: 8px; flex-wrap: wrap; }

/* ---- hamburger menu ---- */
.icon-button {
  display: inline-grid;
  place-items: center;
  width: 42px;
  height: 42px;
  padding: 0;
}
.menu { position: relative; }
.menu-panel {
  position: absolute;
  top: calc(100% + 6px);
  right: 0;
  z-index: 10;
  min-width: 180px;
  padding: 6px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--panel-shadow), 0 8px 24px rgba(0, 0, 0, 0.18);
}
.menu-panel ul { list-style: none; margin: 0; padding: 0; }
.menu-panel button {
  width: 100%;
  text-align: left;
  border-color: transparent;
  background: transparent;
  font-family: var(--font-mono);
}

/* ---- tutorial ---- */
.tutorial {
  width: min(920px, 100vw - 32px);
  height: min(760px, 100vh - 32px);
  max-width: none;
  max-height: none;
  padding: 0;
}
.tutorial[open] { display: flex; flex-direction: column; }
.tutorial-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 12px 10px 20px;
  border-bottom: 1px solid var(--line);
}
.tutorial-head h2 { margin: 0; color: var(--accent); }
.tutorial-layout {
  flex: 1;
  min-height: 0;
  display: grid;
  grid-template-columns: 210px 1fr;
}
.tutorial-nav { padding: 12px; border-right: 1px solid var(--line); overflow-y: auto; }
.tutorial-nav ol { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; }
.tutorial-nav button {
  width: 100%;
  text-align: left;
  border-color: transparent;
  background: transparent;
  color: var(--muted);
  font: 500 0.9rem/1.3 var(--font-mono);
}
.tutorial-nav button[aria-current="true"] { color: var(--accent); border-color: var(--accent); background: var(--bg); }
.tutorial-body { overflow-y: auto; padding: 4px 24px 24px; line-height: 1.6; }
.tutorial-body article { max-width: 68ch; }
.tutorial-body h3 { margin: 16px 0 8px; font: 700 1.3rem/1.3 var(--font-mono); color: var(--accent); }
/* Headings get focus only so reading starts at the new section; they aren't controls. */
.tutorial-body h3:focus { outline: none; }
.tutorial-body h4 { margin: 20px 0 6px; font: 700 1rem/1.3 var(--font-mono); color: var(--accent-2); }
.tutorial-body p, .tutorial-body ul, .tutorial-body ol { margin: 0 0 10px; }
.tutorial-body li { margin-bottom: 6px; }
.tutorial-body code {
  padding: 1px 5px;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--bg);
  font: 0.9em var(--font-mono);
  font-variant-ligatures: none;
  overflow-wrap: anywhere;
}
.tutorial-next { margin-top: 12px; }

@media (max-width: 640px) {
  .tutorial { width: 100vw; height: 100vh; height: 100dvh; margin: 0; border: none; border-radius: 0; }
  .tutorial-layout { grid-template-columns: 1fr; grid-template-rows: auto 1fr; }
  .tutorial-nav { border-right: none; border-bottom: 1px solid var(--line); padding: 8px 12px; }
  .tutorial-nav ol { display: flex; flex-wrap: wrap; gap: 6px; }
  .tutorial-nav button { width: auto; padding: 5px 10px; border-color: var(--line); }
  .tutorial-body { padding: 4px 16px 20px; }
}

@media (prefers-reduced-motion: reduce) {
  h1 .cursor { animation: none; }
  button { transition: none; }
}