:root {
  --bg: #050816;
  --surface: rgba(15, 18, 35, 0.78);
  --surface-2: rgba(25, 29, 52, 0.85);

  --purple: #8b5cf6;
  --purple-light: #a78bfa;
  --cyan: #22d3ee;
  --green: #34d399;
  --red: #fb7185;
  --yellow: #facc15;

  --text: #f8fafc;
  --muted: #94a3b8;

  --border: rgba(255, 255, 255, 0.09);

  --shadow:
    0 25px 70px rgba(0, 0, 0, 0.45);

  --transition:
    0.25s cubic-bezier(.2,.8,.2,1);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;

  background:
    radial-gradient(
      circle at 15% 10%,
      rgba(139, 92, 246, .18),
      transparent 30%
    ),
    radial-gradient(
      circle at 85% 20%,
      rgba(34, 211, 238, .12),
      transparent 30%
    ),
    var(--bg);

  color: var(--text);

  font-family: "Inter", sans-serif;

  overflow-x: hidden;
}

/* BACKGROUND */

.background-grid {
  position: fixed;
  inset: 0;

  pointer-events: none;

  background-image:
    linear-gradient(
      rgba(255,255,255,.025) 1px,
      transparent 1px
    ),
    linear-gradient(
      90deg,
      rgba(255,255,255,.025) 1px,
      transparent 1px
    );

  background-size: 50px 50px;

  mask-image:
    radial-gradient(
      ellipse at center,
      black 25%,
      transparent 80%
    );

  z-index: -2;
}

.glow {
  position: fixed;

  width: 400px;
  height: 400px;

  border-radius: 50%;

  filter: blur(100px);

  pointer-events: none;

  opacity: .12;

  z-index: -1;
}

.glow-purple {
  background: var(--purple);

  top: -150px;
  left: -100px;
}

.glow-cyan {
  background: var(--cyan);

  right: -150px;
  bottom: -150px;
}

/* APP */

.app {
  width: min(1100px, calc(100% - 32px));

  margin: auto;

  padding:
    22px 0
    70px;
}

/* NAVBAR */

.navbar {
  height: 64px;

  display: flex;
  align-items: center;
  justify-content: space-between;

  margin-bottom: 60px;

  padding: 0 18px;

  border: 1px solid var(--border);

  background: rgba(10, 13, 28, .55);

  backdrop-filter: blur(18px);

  border-radius: 18px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;

  color: var(--text);

  text-decoration: none;

  font-family: "Space Grotesk";
  font-weight: 700;
}

.brand-icon {
  width: 36px;
  height: 36px;

  display: grid;
  place-items: center;

  border-radius: 10px;

  background:
    linear-gradient(
      135deg,
      var(--purple),
      var(--cyan)
    );

  font-size: .75rem;
}

.nav-right {
  display: flex;
  align-items: center;
  gap: 18px;
}

.mode-label {
  color: var(--purple-light);

  font-family: "JetBrains Mono";

  font-size: .65rem;

  letter-spacing: .12em;
}

.back-btn {
  color: var(--muted);

  text-decoration: none;

  font-size: .82rem;

  padding: 9px 14px;

  border: 1px solid var(--border);

  border-radius: 9px;

  transition: var(--transition);
}

.back-btn:hover {
  color: white;

  border-color: var(--purple);
}

/* HERO */

.hero {
  text-align: center;

  max-width: 750px;

  margin:
    0 auto
    40px;
}

.badge {
  display: inline-flex;

  padding: 7px 13px;

  border-radius: 99px;

  background: rgba(139, 92, 246, .1);

  border: 1px solid rgba(139, 92, 246, .25);

  color: var(--purple-light);

  font-size: .7rem;

  font-weight: 700;

  letter-spacing: .08em;
}

.hero h1 {
  margin-top: 20px;

  font-family: "Space Grotesk";

  font-size:
    clamp(3.5rem, 10vw, 7rem);

  line-height: .9;

  letter-spacing: -.07em;
}

.hero h1 span {
  background:
    linear-gradient(
      135deg,
      #fff,
      var(--purple-light),
      var(--cyan)
    );

  -webkit-background-clip: text;
  background-clip: text;

  color: transparent;
}

.hero > p {
  margin-top: 24px;

  color: var(--muted);

  font-size: 1.05rem;
}

.hero > p strong {
  color: white;
}

.hero-subtitle {
  margin-top: 8px !important;

  font-size: .82rem !important;

  opacity: .75;
}

/* STATS */

.stats {
  display: grid;

  grid-template-columns:
    repeat(4, 1fr);

  gap: 12px;

  margin-bottom: 30px;
}

.stat-card {
  display: flex;

  align-items: center;

  gap: 14px;

  padding: 17px;

  border-radius: 15px;

  background: var(--surface);

  border: 1px solid var(--border);

  backdrop-filter: blur(16px);

  transition: var(--transition);
}

.stat-card:hover {
  transform: translateY(-3px);

  border-color:
    rgba(139, 92, 246, .35);
}

.stat-icon {
  font-size: 1.3rem;
}

.stat-card strong {
  display: block;

  font-family: "JetBrains Mono";

  font-size: 1.2rem;
}

.stat-card small {
  color: var(--muted);

  font-size: .68rem;
}

/* CONTROLS */

.controls {
  margin-bottom: 30px;
}

.control-title {
  display: flex;

  align-items: baseline;

  gap: 10px;

  margin-bottom: 12px;

  font-weight: 700;
}

.control-title small {
  color: var(--muted);

  font-size: .7rem;
}

.category-row {
  display: flex;

  gap: 8px;

  flex-wrap: wrap;
}

.category-btn {
  padding: 9px 15px;

  border-radius: 99px;

  border: 1px solid var(--border);

  background: rgba(255,255,255,.03);

  color: var(--muted);

  cursor: pointer;

  transition: var(--transition);
}

.category-btn:hover {
  color: white;

  border-color:
    rgba(139,92,246,.4);
}

.category-btn.active {
  background:
    linear-gradient(
      135deg,
      rgba(139,92,246,.25),
      rgba(34,211,238,.1)
    );

  border-color: var(--purple);

  color: white;
}

/* CHAOS */

.chaos-area {
  text-align: center;

  padding: 35px 0 50px;
}

.chaos-core {
  width: 190px;
  height: 190px;

  margin: auto;

  position: relative;

  display: grid;
  place-items: center;

  border-radius: 50%;

  background:
    radial-gradient(
      circle,
      rgba(139,92,246,.2),
      rgba(5,8,22,.95) 65%
    );

  border:
    1px solid rgba(139,92,246,.35);

  box-shadow:
    0 0 70px rgba(139,92,246,.15);

  transition: 1s;
}

.chaos-core.generating {
  animation:
    chaosSpin 1.2s linear infinite;

  box-shadow:
    0 0 90px rgba(139,92,246,.5),
    0 0 140px rgba(34,211,238,.2);
}

.core-ring {
  position: absolute;

  border: 1px solid rgba(167,139,250,.2);

  border-radius: 50%;
}

.ring-one {
  inset: 12px;

  animation:
    rotate 8s linear infinite;
}

.ring-two {
  inset: 28px;

  border-color:
    rgba(34,211,238,.2);

  animation:
    rotateReverse 6s linear infinite;
}

.ring-three {
  inset: 45px;

  border-style: dashed;

  animation:
    rotate 4s linear infinite;
}

.core-content {
  position: relative;

  z-index: 2;

  display: flex;

  flex-direction: column;

  align-items: center;
}

.core-icon {
  font-size: 2.5rem;
}

.core-text {
  margin-top: 5px;

  font-family: "JetBrains Mono";

  font-weight: 700;

  letter-spacing: .15em;
}

.core-content small {
  margin-top: 3px;

  color: var(--muted);

  font-size: .6rem;

  letter-spacing: .2em;
}

/* GENERATE */

.generate-btn {
  margin-top: 35px;

  padding: 15px 27px;

  border: 0;

  border-radius: 12px;

  background:
    linear-gradient(
      135deg,
      var(--purple),
      #6366f1
    );

  color: white;

  font-family: "Space Grotesk";

  font-size: .9rem;

  font-weight: 700;

  cursor: pointer;

  box-shadow:
    0 15px 40px
    rgba(139,92,246,.25);

  transition: var(--transition);
}

.generate-btn:hover {
  transform: translateY(-3px);

  box-shadow:
    0 20px 50px
    rgba(139,92,246,.4);
}

.generate-btn:active {
  transform: scale(.97);
}

.generate-hint {
  margin-top: 12px;

  color: var(--muted);

  font-size: .7rem;
}

/* CHALLENGE */

.challenge-section {
  margin-top: 10px;

  animation:
    challengeIn .5s ease;
}

.hidden {
  display: none !important;
}

.challenge-card {
  padding: 28px;

  border-radius: 22px;

  background:
    linear-gradient(
      145deg,
      rgba(22,25,48,.9),
      rgba(12,15,30,.9)
    );

  border: 1px solid
    rgba(139,92,246,.25);

  box-shadow: var(--shadow);
}

.challenge-header {
  display: flex;

  justify-content: space-between;

  gap: 15px;

  flex-wrap: wrap;
}

.category-badge,
.difficulty-badge {
  display: inline-block;

  padding: 6px 10px;

  border-radius: 7px;

  font-family: "JetBrains Mono";

  font-size: .65rem;

  font-weight: 700;
}

.category-badge {
  color: var(--cyan);

  background:
    rgba(34,211,238,.1);
}

.difficulty-badge {
  margin-left: 6px;

  color: var(--yellow);

  background:
    rgba(250,204,21,.1);
}

.challenge-meta {
  display: flex;

  gap: 10px;

  color: var(--green);

  font-family: "JetBrains Mono";

  font-size: .72rem;
}

.challenge-card h2 {
  margin-top: 22px;

  font-family: "Space Grotesk";

  font-size: 1.8rem;
}

.challenge-description {
  margin-top: 8px;

  color: var(--muted);

  line-height: 1.7;
}

/* WORKSPACE */

.challenge-workspace {
  margin-top: 25px;

  padding: 22px;

  border-radius: 14px;

  background:
    rgba(0,0,0,.25);

  border: 1px solid var(--border);
}

.code-block {
  padding: 18px;

  overflow-x: auto;

  border-radius: 10px;

  background: #070a16;

  color: #dbeafe;

  font-family: "JetBrains Mono";

  font-size: .8rem;

  line-height: 1.7;
}

.answer-input {
  width: 100%;

  padding: 13px 15px;

  margin-top: 14px;

  border-radius: 9px;

  border: 1px solid var(--border);

  outline: none;

  background: rgba(255,255,255,.04);

  color: white;

  font-family: "JetBrains Mono";
}

.answer-input:focus {
  border-color: var(--purple);
}

.option-grid {
  display: grid;

  grid-template-columns:
    repeat(2, 1fr);

  gap: 10px;
}

.option-btn {
  padding: 14px;

  text-align: left;

  border-radius: 10px;

  border: 1px solid var(--border);

  background: rgba(255,255,255,.03);

  color: var(--text);

  cursor: pointer;

  transition: var(--transition);
}

.option-btn:hover {
  border-color: var(--purple);
}

.option-btn.selected {
  background:
    rgba(139,92,246,.15);

  border-color: var(--purple);
}

.option-btn.correct {
  background:
    rgba(52,211,153,.15);

  border-color: var(--green);
}

.option-btn.wrong {
  background:
    rgba(251,113,133,.15);

  border-color: var(--red);
}

/* RESULT */

.result-message {
  margin-top: 18px;

  padding: 13px 15px;

  border-radius: 10px;

  font-weight: 600;
}

.result-message.success {
  color: var(--green);

  background:
    rgba(52,211,153,.1);

  border: 1px solid
    rgba(52,211,153,.25);
}

.result-message.error {
  color: var(--red);

  background:
    rgba(251,113,133,.1);

  border: 1px solid
    rgba(251,113,133,.25);
}

/* ACTIONS */

.challenge-actions {
  display: flex;

  gap: 10px;

  margin-top: 20px;
}

.submit-btn,
.skip-btn {
  padding: 12px 18px;

  border-radius: 9px;

  cursor: pointer;

  font-weight: 700;

  transition: var(--transition);
}

.submit-btn {
  border: 0;

  background:
    linear-gradient(
      135deg,
      var(--green),
      #10b981
    );

  color: #03140d;

  flex: 1;
}

.submit-btn:hover {
  transform: translateY(-2px);
}

.skip-btn {
  border: 1px solid var(--border);

  background: transparent;

  color: var(--muted);
}

.skip-btn:hover {
  color: white;

  border-color: var(--red);
}

/* RECENT */

.recent-section {
  margin-top: 50px;
}

.section-heading span {
  display: block;

  font-family: "JetBrains Mono";

  font-size: .7rem;

  letter-spacing: .15em;

  color: var(--purple-light);
}

.section-heading small {
  display: block;

  margin-top: 4px;

  color: var(--muted);

  font-size: .75rem;
}

.recent-list {
  margin-top: 15px;

  display: grid;

  gap: 8px;
}

.recent-item {
  display: flex;

  justify-content: space-between;

  align-items: center;

  padding: 12px 15px;

  border-radius: 10px;

  background: rgba(255,255,255,.03);

  border: 1px solid var(--border);

  font-size: .78rem;
}

.recent-item small {
  color: var(--muted);
}

.empty-state {
  padding: 30px;

  text-align: center;

  color: var(--muted);

  font-size: .8rem;

  border: 1px dashed var(--border);

  border-radius: 12px;
}

/* FOOTER */

footer {
  display: flex;

  justify-content: center;

  gap: 8px;

  margin-top: 60px;

  color: var(--muted);

  font-size: .7rem;
}

/* ANIMATIONS */

@keyframes rotate {
  to {
    transform: rotate(360deg);
  }
}

@keyframes rotateReverse {
  to {
    transform: rotate(-360deg);
  }
}

@keyframes chaosSpin {
  0% {
    transform: rotate(0) scale(1);
  }

  50% {
    transform: rotate(180deg) scale(1.08);
  }

  100% {
    transform: rotate(360deg) scale(1);
  }
}

@keyframes challengeIn {
  from {
    opacity: 0;
    transform: translateY(20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* RESPONSIVE */

@media (max-width: 700px) {

  .app {
    width: min(100% - 20px, 600px);
  }

  .navbar {
    margin-bottom: 40px;
  }

  .mode-label {
    display: none;
  }

  .hero h1 {
    font-size: 4rem;
  }

  .stats {
    grid-template-columns:
      repeat(2, 1fr);
  }

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

  .challenge-card {
    padding: 20px;
  }
}

@media (max-width: 430px) {

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

  .stat-card {
    padding: 12px;
  }

  .hero h1 {
    font-size: 3.2rem;
  }

  .chaos-core {
    width: 160px;
    height: 160px;
  }
}