:root {
  --bg: #f7f7f5;
  --panel: #ffffff;
  --panel-subtle: #f0efe9;
  --text: #1f1f1a;
  --muted: #5d5f52;
  --border: #d6d8cc;
  --accent: #0f766e;
  --accent-strong: #0b5a54;
  --danger: #8f1f1f;
  --warn: #8a5600;
  --ok: #1d6e2e;
  --radius: 12px;
  --shadow: 0 2px 12px rgba(25, 27, 16, 0.08);
  --mono: "Iosevka Web", "Cascadia Mono", "Consolas", "Liberation Mono", monospace;
  --ui: "Atkinson Hyperlegible", "Segoe UI", "Helvetica Neue", sans-serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  width: 100%;
  min-height: 100%;
}

body {
  font-family: var(--ui);
  color: var(--text);
  background:
    radial-gradient(circle at 10% 10%, rgba(42, 166, 137, 0.11), transparent 30%),
    radial-gradient(circle at 85% 15%, rgba(240, 179, 74, 0.13), transparent 24%),
    linear-gradient(180deg, #fcfcfa 0%, #f4f3ef 100%);
}

#app {
  max-width: 1720px;
  margin: 0 auto;
  padding: 16px;
}

.error-panel {
  position: relative;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: color-mix(in srgb, var(--panel) 94%, #fff7e0);
  box-shadow: var(--shadow);
  margin-bottom: 10px;
}

.error-panel[data-has-errors="true"] {
  border-color: #e2b66f;
}

.error-panel-summary {
  display: flex;
  align-items: center;
  gap: 10px;
  list-style: none;
  cursor: pointer;
  padding: 8px 10px;
}

.error-panel-summary::-webkit-details-marker {
  display: none;
}

.error-panel-title {
  font-weight: 600;
}

.error-panel-count {
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 2px 8px;
  font-size: 0.8rem;
  background: #fff;
}

.error-panel[data-has-errors="true"] .error-panel-count {
  border-color: #d3944f;
  color: #7a3d00;
  background: #fff5e8;
}

.error-panel-clear {
  margin-left: auto;
  font-size: 0.82rem;
  padding: 5px 9px;
}

.error-panel-list {
  border-top: 1px solid var(--border);
  padding: 8px 10px;
  max-height: 220px;
  overflow: auto;
  display: grid;
  gap: 8px;
}

.error-panel-item {
  border: 1px solid #e6d0ac;
  border-radius: 8px;
  background: #fffaf2;
  padding: 8px;
}

.error-panel-item-header {
  margin-bottom: 4px;
}

.error-panel-stack {
  margin-top: 6px;
  max-height: 120px;
}

.shell {
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 12px;
  min-height: calc(100vh - 32px);
}

.topbar {
  display: grid;
  gap: 8px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--panel) 92%, #eef6f4);
  box-shadow: var(--shadow);
}

.topbar-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
}

.topbar-row-utility {
  border-top: 1px dashed color-mix(in srgb, var(--border) 78%, #bfd0c6);
  padding-top: 8px;
}

.topbar h1 {
  margin: 0;
  font-size: 1.1rem;
  letter-spacing: 0.2px;
}

.spacer {
  flex: 1;
}

.control,
button,
select,
textarea,
input {
  font: inherit;
}

button,
select,
.tab-button {
  border: 1px solid var(--border);
  border-radius: 9px;
  background: var(--panel);
  color: var(--text);
  padding: 7px 10px;
}

button:hover,
select:hover,
.tab-button:hover {
  border-color: #aeb3a0;
}

button.primary {
  border-color: transparent;
  background: var(--accent);
  color: #fff;
}

button.primary:hover {
  background: var(--accent-strong);
}

button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.primary-action-group,
.utility-action-group {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 6px;
  align-items: center;
}

.primary-action-group button,
.utility-action-group button {
  white-space: nowrap;
}

.challenge-picker {
  display: grid;
  gap: 4px;
  font-size: 0.88rem;
}

.danger-soft {
  border-color: #d5a1a1;
  background: color-mix(in srgb, #fff2f2 90%, #ffd5d5);
  color: #862c2c;
}

.danger-soft:hover {
  border-color: #bf7f7f;
  background: color-mix(in srgb, #ffeaea 82%, #ffc8c8);
}

.workspace {
  display: grid;
  grid-template-columns: minmax(320px, 46%) minmax(420px, 54%);
  gap: 12px;
  min-height: 0;
}

.panel {
  min-height: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.problem-panel {
  display: grid;
  grid-template-rows: auto 1fr;
  overflow: hidden;
}

.problem-header {
  border-bottom: 1px solid var(--border);
  padding: 12px 14px;
  background: var(--panel-subtle);
}

.problem-header h2 {
  margin: 0;
  font-size: 1.05rem;
}

.problem-meta {
  margin-top: 6px;
  color: var(--muted);
  font-size: 0.93rem;
}

.problem-content {
  padding: 14px;
  overflow: auto;
  line-height: 1.45;
}

.problem-content pre,
.problem-content code,
.signature,
.mono {
  font-family: var(--mono);
}

.problem-content pre {
  background: #101112;
  color: #e7e7e7;
  padding: 10px;
  border-radius: 8px;
  overflow-x: auto;
}

.problem-content table {
  width: 100%;
  border-collapse: collapse;
}

.problem-content th,
.problem-content td {
  border: 1px solid var(--border);
  padding: 6px 8px;
  text-align: left;
  vertical-align: top;
}

.editor-panel {
  display: grid;
  grid-template-rows: auto minmax(220px, 1fr) auto auto;
  min-height: 0;
  overflow: hidden;
}

.editor-toolbar {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
  background: var(--panel-subtle);
}

.status-badge {
  border-radius: 999px;
  font-size: 0.82rem;
  padding: 4px 9px;
  border: 1px solid var(--border);
  background: #fff;
}

.share-feedback {
  min-height: 1.2em;
  font-size: 0.82rem;
  color: var(--muted);
  max-width: 280px;
}

.share-feedback[data-tone="success"] {
  color: var(--ok);
}

.share-feedback[data-tone="warning"] {
  color: var(--warn);
}

.status-idle {
  color: var(--muted);
}

.status-running {
  color: var(--warn);
  border-color: #e0be7b;
  background: #fff8e9;
}

.status-success {
  color: var(--ok);
  border-color: #84c696;
  background: #effff3;
}

.status-failure {
  color: var(--danger);
  border-color: #e0a3a3;
  background: #fff1f1;
}

.editor-host {
  min-height: 0;
  background: #fcfcf9;
}

.cm-editor {
  height: 100%;
  font-family: var(--mono);
  font-size: 0.95rem;
  border-bottom: 1px solid var(--border);
}

.custom-tests {
  border-top: 1px solid var(--border);
  padding: 10px 12px;
  display: grid;
  gap: 6px;
}

.custom-tests textarea {
  width: 100%;
  min-height: 86px;
  resize: vertical;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fafaf8;
  font-family: var(--mono);
  font-size: 0.86rem;
  padding: 8px;
}

.results {
  border-top: 1px solid var(--border);
  display: grid;
  grid-template-columns: 1fr;
  min-height: 0;
}

.results-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  min-height: 220px;
}

.results-panel {
  min-height: 0;
  overflow: auto;
  padding: 10px 12px;
}

.results-panel + .results-panel {
  border-left: 1px solid var(--border);
}

.result-item {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px;
  background: #fcfcfb;
  margin-bottom: 8px;
}

.result-item.pass {
  border-color: #98d5a4;
  background: #f2fff5;
}

.result-item.fail {
  border-color: #e8afaf;
  background: #fff5f5;
}

.result-details {
  margin-top: 8px;
}

.result-details > summary {
  cursor: pointer;
  font-size: 0.83rem;
  font-weight: 600;
  color: #325d58;
}

.result-input-block {
  margin-top: 8px;
  max-height: 150px;
}

.result-row {
  font-size: 0.86rem;
  color: var(--muted);
}

.output-block {
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #101112;
  color: #ebf0eb;
  font-family: var(--mono);
  font-size: 0.82rem;
  padding: 8px;
  white-space: pre-wrap;
  max-height: 220px;
  overflow: auto;
}

.diagnostics {
  border: 1px solid #edc8c8;
  border-radius: 8px;
  background: #fff2f2;
  color: #601f1f;
  padding: 8px;
  font-size: 0.86rem;
}

.tabs {
  display: none;
  align-items: center;
  gap: 6px;
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 4px;
  background: #f4f6ef;
}

.tabs-label {
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #5b6150;
  padding: 0 4px 0 6px;
}

.tab-button {
  border-radius: 999px;
  padding: 5px 10px;
  font-size: 0.83rem;
  border-color: transparent;
  background: transparent;
}

.tab-button.active {
  background: var(--accent);
  color: #fff;
  border-color: transparent;
}

.hidden-mobile {
  display: block;
}

.settings-dialog {
  width: min(680px, calc(100vw - 32px));
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 0;
  box-shadow: 0 20px 60px rgba(15, 23, 42, 0.24);
}

.settings-dialog::backdrop {
  background: rgba(9, 14, 28, 0.42);
}

.settings-dialog-body {
  display: grid;
  gap: 14px;
  padding: 16px;
  background: linear-gradient(180deg, #ffffff, #f6f8f7);
}

.settings-dialog-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.settings-dialog-header h2 {
  margin: 0;
  font-size: 1.1rem;
}

.settings-section {
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  background: var(--panel);
  display: grid;
  gap: 10px;
}

.settings-section h3 {
  margin: 0;
}

.settings-section label {
  display: grid;
  gap: 5px;
  font-size: 0.92rem;
}

.settings-inline-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
}

.dialog-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
}

.help-dialog .settings-section h3 {
  margin: 0;
  font-size: 0.98rem;
}

.tool-window {
  position: fixed;
  display: grid;
  grid-template-rows: auto 1fr;
  border: 1px solid color-mix(in srgb, var(--border) 85%, #6e7b8a);
  border-radius: 12px;
  background: color-mix(in srgb, var(--panel) 90%, #f2f5f5);
  box-shadow:
    0 20px 44px rgba(19, 27, 30, 0.24),
    0 3px 12px rgba(19, 27, 30, 0.16);
  overflow: hidden;
  min-width: 260px;
  min-height: 180px;
  contain: paint;
  transform: translate3d(0, 0, 0);
}

.tool-window[hidden] {
  display: none !important;
}

.tool-window-titlebar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 8px 10px;
  border-bottom: 1px solid color-mix(in srgb, var(--border) 86%, #96a2ae);
  background: linear-gradient(
    180deg,
    color-mix(in srgb, #ffffff 74%, rgba(212, 238, 233, 0.8)),
    color-mix(in srgb, #f2f6f5 76%, rgba(212, 238, 233, 0.6))
  );
  backdrop-filter: blur(12px) saturate(1.25);
  cursor: move;
  user-select: none;
  touch-action: none;
}

.tool-window.is-dragging {
  will-change: transform;
}

.tool-window.is-interacting .tool-window-titlebar {
  backdrop-filter: none;
}

.tool-window-title-group {
  min-width: 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.tool-window-title {
  font-size: 0.88rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  white-space: nowrap;
  text-overflow: ellipsis;
  overflow: hidden;
}

.tool-window-controls {
  display: inline-flex;
  gap: 6px;
}

.tool-window-control {
  border: 1px solid color-mix(in srgb, var(--border) 85%, #8ea0b0);
  background: color-mix(in srgb, var(--panel) 92%, #eff5f3);
  padding: 5px 8px;
  font-size: 0.78rem;
  border-radius: 8px;
}

.tool-window-control:hover {
  border-color: #8fa3b2;
}

.tool-window-control-close {
  background: color-mix(in srgb, #fff6f6 86%, #ffdede);
  border-color: #d8a4a4;
}

.tool-window-body {
  min-height: 0;
  background: #f6f7f2;
  position: relative;
  overflow: hidden;
}

.reference-window-frame {
  width: 100%;
  height: 100%;
  border: 0;
  background: #f6f7f2;
  position: relative;
  z-index: 1;
}

.tool-window-interaction-overlay {
  position: absolute;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 12px;
  background: rgba(244, 247, 242, 0.94);
  color: #44525d;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  z-index: 2;
  pointer-events: none;
}

.tool-window.is-interacting .tool-window-interaction-overlay {
  display: flex;
}

.tool-window.is-interacting .reference-window-frame {
  visibility: hidden;
}

.tool-window-resize-handle {
  position: absolute;
  z-index: 3;
}

.tool-window-resize-handle.handle-n,
.tool-window-resize-handle.handle-s {
  left: 10px;
  right: 10px;
  height: 10px;
}

.tool-window-resize-handle.handle-n {
  top: -5px;
  cursor: ns-resize;
}

.tool-window-resize-handle.handle-s {
  bottom: -5px;
  cursor: ns-resize;
}

.tool-window-resize-handle.handle-e,
.tool-window-resize-handle.handle-w {
  top: 10px;
  bottom: 10px;
  width: 10px;
}

.tool-window-resize-handle.handle-e {
  right: -5px;
  cursor: ew-resize;
}

.tool-window-resize-handle.handle-w {
  left: -5px;
  cursor: ew-resize;
}

.tool-window-resize-handle.handle-ne,
.tool-window-resize-handle.handle-nw,
.tool-window-resize-handle.handle-se,
.tool-window-resize-handle.handle-sw {
  width: 14px;
  height: 14px;
}

.tool-window-resize-handle.handle-ne {
  top: -7px;
  right: -7px;
  cursor: nesw-resize;
}

.tool-window-resize-handle.handle-nw {
  top: -7px;
  left: -7px;
  cursor: nwse-resize;
}

.tool-window-resize-handle.handle-se {
  right: -7px;
  bottom: -7px;
  cursor: nwse-resize;
}

.tool-window-resize-handle.handle-sw {
  left: -7px;
  bottom: -7px;
  cursor: nesw-resize;
}

@media (max-width: 1100px) {
  .workspace {
    grid-template-columns: 1fr;
    grid-template-rows: minmax(260px, 46vh) minmax(420px, 1fr);
  }

  .tabs {
    display: flex;
    order: 4;
  }

  body[data-mobile-view="problem"] .editor-panel,
  body[data-mobile-view="editor"] .problem-panel {
    display: none;
  }

  .challenge-picker {
    order: 5;
  }

  #run-btn,
  #format-btn,
  #share-btn,
  #reference-btn,
  #run-status,
  #share-feedback {
    order: 6;
  }

  .primary-action-group {
    order: 6;
  }

  #settings-btn,
  #help-btn,
  #reset-btn {
    order: 7;
  }

  .utility-action-group {
    order: 7;
    width: 100%;
    justify-content: flex-end;
  }

  #share-feedback {
    max-width: unset;
    width: 100%;
  }

  .results-grid {
    grid-template-columns: 1fr;
  }

  .results-panel + .results-panel {
    border-left: 0;
    border-top: 1px solid var(--border);
  }
}