/* Theme & base — Nyocha Ọnụọdụ */
:root {
  --font-sans: "DM Sans", system-ui, sans-serif;
  --font-display: "Fraunces", Georgia, serif;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow: 0 18px 50px rgba(15, 23, 42, 0.12);
  --transition: 0.28s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="light"] {
  --bg: #f4f6fb;
  --bg-elevated: #ffffff;
  --text: #0f172a;
  --text-muted: #64748b;
  --border: rgba(15, 23, 42, 0.08);
  --accent: #0d9488;
  --accent-hover: #0f766e;
  --error-bg: rgba(220, 38, 38, 0.12);
  --error-text: #b91c1c;
  --warn-bg: rgba(217, 119, 6, 0.12);
  --success-bg: rgba(13, 148, 136, 0.14);
  --success-border: rgba(13, 148, 136, 0.35);
  --success-text: #0f766e;
  --highlight: rgba(13, 148, 136, 0.15);
  --mesh-1: rgba(13, 148, 136, 0.15);
  --mesh-2: rgba(99, 102, 241, 0.12);
}

[data-theme="dark"] {
  --bg: #0c1222;
  --bg-elevated: #121a2e;
  --text: #e8edf7;
  --text-muted: #94a3b8;
  --border: rgba(255, 255, 255, 0.08);
  --accent: #2dd4bf;
  --accent-hover: #5eead4;
  --error-bg: rgba(248, 113, 113, 0.15);
  --error-text: #fecaca;
  --warn-bg: rgba(251, 191, 36, 0.12);
  --success-bg: rgba(45, 212, 191, 0.12);
  --success-border: rgba(45, 212, 191, 0.35);
  --success-text: #5eead4;
  --highlight: rgba(45, 212, 191, 0.12);
  --mesh-1: rgba(45, 212, 191, 0.12);
  --mesh-2: rgba(129, 140, 248, 0.1);
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.55;
  color: var(--text);
  background: var(--bg);
  transition: background var(--transition), color var(--transition);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: auto;
  width: 1px;
  height: 1px;
  overflow: hidden;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
  width: auto;
  height: auto;
  padding: 0.5rem 1rem;
  background: var(--accent);
  color: #fff;
  border-radius: var(--radius-sm);
  z-index: 100;
}

.app-bg {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(ellipse 80% 50% at 10% -10%, var(--mesh-1), transparent 55%),
    radial-gradient(ellipse 60% 40% at 100% 0%, var(--mesh-2), transparent 50%),
    var(--bg);
  transition: opacity var(--transition);
}

.site-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1.25rem clamp(1rem, 4vw, 2.5rem);
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--bg-elevated) 85%, transparent);
  backdrop-filter: blur(12px);
  animation: slideDown 0.5s var(--transition) both;
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.brand-mark {
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
  background: var(--highlight);
  border-radius: 12px;
  border: 1px solid var(--border);
}

.brand-title {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(1.25rem, 2.5vw, 1.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.brand-sub {
  margin: 0;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

/* Theme toggle */
.toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  cursor: pointer;
  user-select: none;
}

.toggle-input {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}

.toggle-track {
  width: 48px;
  height: 26px;
  border-radius: 999px;
  background: var(--border);
  position: relative;
  transition: background var(--transition);
}

.toggle-thumb {
  position: absolute;
  top: 3px;
  left: 3px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--bg-elevated);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.15);
  transition: transform var(--transition);
}

.toggle-input:checked + .toggle-track {
  background: var(--accent);
}

.toggle-input:checked + .toggle-track .toggle-thumb {
  transform: translateX(22px);
}

.toggle-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  min-width: 2.5rem;
}

/* Layout */
.layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-template-rows: auto auto;
  grid-template-areas:
    "editor output"
    "sidebar sidebar";
  gap: 1rem;
  padding: 1rem clamp(1rem, 3vw, 2rem) 2rem;
  max-width: 1400px;
  margin: 0 auto;
}

@media (min-width: 1024px) {
  .layout {
    grid-template-columns: 1fr 1fr minmax(260px, 320px);
    grid-template-rows: 1fr;
    grid-template-areas: "editor output sidebar";
    align-items: start;
    min-height: calc(100vh - 140px);
  }
}

.panel {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1rem 1.15rem;
  animation: fadeIn 0.45s var(--transition) both;
}

.panel:nth-child(1) {
  animation-delay: 0.05s;
}
.panel:nth-child(2) {
  animation-delay: 0.1s;
}
.panel:nth-child(3) {
  animation-delay: 0.15s;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.panel-editor {
  grid-area: editor;
}

.panel-output {
  grid-area: output;
}

.panel-sidebar {
  grid-area: sidebar;
}

.panel-head {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.panel-title {
  margin: 0;
  font-size: 0.95rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.realtime {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.8rem;
  color: var(--text-muted);
  cursor: pointer;
}

.realtime input {
  accent-color: var(--accent);
}

.badge {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.25rem 0.6rem;
  border-radius: 999px;
  background: var(--highlight);
  color: var(--accent);
}

/* Text input */
.text-input {
  width: 100%;
  min-height: 280px;
  padding: 1rem 1.1rem;
  font-family: var(--font-sans);
  font-size: 1.05rem;
  line-height: 1.65;
  color: var(--text);
  background: color-mix(in srgb, var(--bg) 40%, var(--bg-elevated));
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  resize: vertical;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.text-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--highlight);
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 0.85rem;
}

.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  padding: 0.55rem 1.1rem;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition:
    transform 0.15s ease,
    background var(--transition),
    border-color var(--transition),
    opacity var(--transition);
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn:not(:disabled):active {
  transform: scale(0.98);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  border-color: color-mix(in srgb, var(--accent) 80%, #000);
  overflow: hidden;
}

.btn-primary:hover:not(:disabled) {
  background: var(--accent-hover);
}

.btn-shine {
  position: absolute;
  inset: 0;
  background: linear-gradient(105deg, transparent 40%, rgba(255, 255, 255, 0.25) 50%, transparent 60%);
  transform: translateX(-100%);
  transition: transform 0.6s ease;
}

.btn-primary:hover:not(:disabled) .btn-shine {
  transform: translateX(100%);
}

.btn-secondary {
  background: transparent;
  color: var(--text);
  border-color: var(--border);
}

.btn-secondary:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent);
}

.btn-ghost {
  background: transparent;
  color: var(--text-muted);
  border-color: var(--border);
  padding: 0.45rem 0.75rem;
  font-size: 0.85rem;
}

.btn-ghost:hover {
  color: var(--accent);
  border-color: var(--accent);
}

.btn-icon {
  font-size: 1rem;
}

.hint {
  margin: 0.5rem 0 0;
  font-size: 0.8rem;
  color: var(--text-muted);
  min-height: 1.2em;
}

.grammar-success {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  margin-bottom: 0.75rem;
  padding: 0.75rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--success-border);
  background: var(--success-bg);
  color: var(--text);
  animation: successIn 0.4s var(--transition) both;
}

.grammar-success[hidden] {
  display: none;
}

@keyframes successIn {
  from {
    opacity: 0;
    transform: translateY(-4px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.grammar-success-icon {
  flex-shrink: 0;
  display: grid;
  place-items: center;
  width: 1.75rem;
  height: 1.75rem;
  border-radius: 999px;
  background: var(--accent);
  color: #fff;
  font-size: 0.95rem;
  font-weight: 700;
  line-height: 1;
}

.grammar-success-msg {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.45;
}

.grammar-success-msg strong {
  display: block;
  color: var(--success-text);
  font-weight: 600;
  margin-bottom: 0.15rem;
}

.grammar-success-en {
  display: block;
  color: var(--text-muted);
  font-size: 0.88rem;
}

/* Highlight output */
.output-wrap {
  min-height: 200px;
  border-radius: var(--radius-sm);
  border: 1px dashed var(--border);
  background: color-mix(in srgb, var(--bg) 35%, var(--bg-elevated));
  transition: border-color var(--transition);
}

.highlight-output {
  min-height: 200px;
  padding: 1rem 1.1rem;
  font-size: 1.05rem;
  line-height: 1.75;
  white-space: pre-wrap;
  word-break: break-word;
}

.highlight-output.empty {
  color: var(--text-muted);
  font-style: italic;
}

.highlight-output.empty::before {
  content: "Results appear here after checking…";
}

mark.hl-error,
mark.hl-warn {
  color: inherit;
  font: inherit;
}

.hl-error {
  position: relative;
  padding: 0 2px;
  border-radius: 4px;
  background: var(--error-bg);
  color: inherit;
  text-decoration: underline;
  text-decoration-style: wavy;
  text-decoration-color: var(--error-text);
  text-underline-offset: 3px;
  cursor: help;
  transition: background var(--transition);
}

.hl-error:hover,
.hl-error:focus {
  background: color-mix(in srgb, var(--error-bg) 70%, var(--accent));
  outline: none;
}

.hl-warn {
  padding: 0 2px;
  border-radius: 4px;
  background: var(--warn-bg);
  text-decoration: underline dotted;
  text-underline-offset: 3px;
  cursor: help;
}

/* Tooltip (title attribute enhanced via data) */
.issue-list {
  list-style: none;
  margin: 0;
  padding: 0;
  max-height: min(420px, 50vh);
  overflow-y: auto;
}

.issue-item {
  padding: 0.65rem 0.75rem;
  margin-bottom: 0.5rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: color-mix(in srgb, var(--bg) 30%, var(--bg-elevated));
  font-size: 0.88rem;
  animation: issueIn 0.35s ease both;
}

@keyframes issueIn {
  from {
    opacity: 0;
    transform: translateX(6px);
  }
}

.issue-item strong {
  display: block;
  color: var(--error-text);
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.issue-item .suggestion {
  color: var(--accent);
  font-weight: 500;
}

.issue-item .explain {
  color: var(--text-muted);
  font-size: 0.82rem;
  margin-top: 0.35rem;
}

.empty-sidebar {
  margin: 0;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.empty-sidebar[hidden] {
  display: none;
}

.site-footer {
  padding: 1rem clamp(1rem, 3vw, 2rem) 2rem;
  max-width: 1400px;
  margin: 0 auto;
  text-align: center;
  font-size: 0.78rem;
  color: var(--text-muted);
}

.site-footer p {
  margin: 0;
  max-width: 56ch;
  margin-inline: auto;
}

@media (max-width: 1023px) {
  .layout {
    grid-template-columns: 1fr;
    grid-template-areas:
      "editor"
      "output"
      "sidebar";
  }

  .issue-list {
    max-height: none;
  }
}