:root {
  --bg-1: #160606;
  --bg-2: #2a0c0c;
  --panel: #3a1212;
  --panel-soft: #471717;
  --border: #7a3232;
  --text: #f8eaea;
  --muted: #dfbdbd;
  --accent: #cb5a5a;
  --accent-strong: #e17777;
  --success: #7fd79f;
  --error: #ffaaaa;
  --warning: #ffd596;
}

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

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 15% 10%, #5a1a1a 0%, rgba(90, 26, 26, 0) 42%),
    radial-gradient(circle at 84% 78%, #3f1111 0%, rgba(63, 17, 17, 0) 39%),
    linear-gradient(135deg, var(--bg-1), var(--bg-2));
  display: grid;
  place-items: center;
  padding: 1rem;
}

.app-shell {
  width: min(860px, 100%);
  display: grid;
  gap: 1rem;
}

.app-header,
.panel {
  background: linear-gradient(165deg, rgba(255, 255, 255, 0.05), rgba(255, 255, 255, 0.02));
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.25);
}

.app-header {
  padding: 1.2rem 1.4rem;
}

.app-header h1 {
  margin: 0;
  font-size: clamp(1.5rem, 3vw, 2rem);
}

.app-header p {
  margin: 0.55rem 0 0;
  color: var(--muted);
}

.panel {
  padding: 1rem 1.1rem;
  background-color: rgba(58, 18, 18, 0.92);
}

.controls-panel {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: end;
  gap: 0.8rem;
}

.field {
  display: grid;
  gap: 0.35rem;
}

label {
  font-weight: 600;
}

select,
input,
button {
  font: inherit;
}

select {
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--panel-soft);
  padding: 0.55rem 0.7rem;
}

select:focus-visible,
button:focus-visible {
  outline: 2px solid var(--accent-strong);
  outline-offset: 2px;
}

button {
  border: 1px solid #a44646;
  border-radius: 10px;
  color: #fff2f2;
  background: linear-gradient(180deg, #b34747, #8f3030);
  padding: 0.58rem 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 120ms ease, filter 120ms ease;
}

button:hover:not(:disabled) {
  filter: brightness(1.1);
}

button:active:not(:disabled) {
  transform: translateY(1px);
}

button:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.problem-panel h2 {
  margin: 0 0 0.7rem;
}

.problem-prompt {
  margin: 0;
  font-size: 1.04rem;
  line-height: 1.45;
}

.problem-meta {
  margin: 0.7rem 0 1rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.tutorial-section {
  margin: 0.2rem 0 1rem;
  padding: 0.8rem;
  border: 1px solid #8a3e3e;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.04);
}

.tutorial-section h3 {
  margin: 0;
  font-size: 1rem;
}

.tutorial-progress {
  margin: 0.45rem 0 0.7rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.tutorial-form {
  display: grid;
  gap: 0.65rem;
}

.tutorial-question {
  margin: 0;
  font-weight: 600;
}

.tutorial-options {
  display: grid;
  gap: 0.45rem;
}

.tutorial-option {
  display: grid;
  grid-template-columns: auto 1fr;
  align-items: start;
  gap: 0.5rem;
  padding: 0.5rem 0.6rem;
  border: 1px solid #7c3535;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.03);
}

.tutorial-option input[type="radio"] {
  margin-top: 0.2rem;
}

.tutorial-option span {
  line-height: 1.35;
}

.tutorial-feedback {
  margin: 0.8rem 0 0;
  min-height: 1.1em;
  font-weight: 600;
}

.tutorial-feedback.info {
  color: var(--muted);
}

.tutorial-feedback.success {
  color: var(--success);
}

.tutorial-feedback.error {
  color: var(--error);
}

.answer-form {
  display: grid;
  gap: 0.65rem;
}

.answer-label {
  margin: 0;
  font-weight: 600;
}

.answer-options {
  display: grid;
  gap: 0.45rem;
}

.answer-option {
  display: grid;
  grid-template-columns: auto 1fr;
  align-items: start;
  gap: 0.5rem;
  padding: 0.5rem 0.6rem;
  border: 1px solid #7c3535;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.03);
}

.answer-option input[type="radio"] {
  margin-top: 0.2rem;
}

.answer-option span {
  line-height: 1.35;
}

.problem-actions {
  margin-top: 0.8rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.hint {
  margin: 0.95rem 0 0;
  padding: 0.6rem 0.75rem;
  border-radius: 10px;
  border: 1px solid #8c3b3b;
  background: rgba(255, 255, 255, 0.05);
  color: #ffe8b9;
}

.feedback {
  margin: 0.95rem 0 0;
  min-height: 1.2em;
  font-weight: 600;
}

.feedback.info {
  color: var(--muted);
}

.feedback.success {
  color: var(--success);
}

.feedback.error {
  color: var(--error);
}

.feedback.warning {
  color: var(--warning);
}

@media (max-width: 640px) {
  .controls-panel {
    grid-template-columns: 1fr;
  }
}