:root {
  --bg: #101827;
  --card: #17233a;
  --text: #f4f7fb;
  --muted: #b9c6d8;
  --accent: #f5c542;
  --ok: #44d07b;
  --bad: #ff6b6b;
  --line: #2c3b58;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: radial-gradient(circle at top, #24395f, var(--bg));
  color: var(--text);
}
header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: center;
  padding: 1rem 1.5rem;
  background: rgba(16, 24, 39, 0.94);
  border-bottom: 1px solid var(--line);
}
h1 { margin: 0; font-size: clamp(1.4rem, 3vw, 2.3rem); }
header p { margin: .2rem 0 0; color: var(--muted); }
.status {
  min-width: 220px;
  padding: .8rem 1rem;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #0d1423;
}
.status strong { display: block; margin-top: .2rem; color: var(--accent); letter-spacing: .2rem; }
main { max-width: 980px; margin: 0 auto; padding: 1.5rem; }
.card {
  margin: 1rem 0;
  padding: 1.3rem;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: rgba(23, 35, 58, 0.96);
  box-shadow: 0 12px 30px rgba(0,0,0,.18);
}
.card h2 { margin-top: 0; }
.theory { border-left: 6px solid #62a8ff; }
.task { border-left: 6px solid var(--accent); }
.vault { border-left: 6px solid var(--ok); }
pre, code, textarea {
  font-family: "Consolas", "Courier New", monospace;
}
pre {
  overflow-x: auto;
  background: #0d1423;
  padding: 1rem;
  border-radius: 12px;
  border: 1px solid var(--line);
}
textarea {
  width: 100%;
  min-height: 150px;
  padding: 1rem;
  color: var(--text);
  background: #0d1423;
  border: 1px solid var(--line);
  border-radius: 12px;
  font-size: 1rem;
}
input {
  padding: .55rem .7rem;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: #f7f7f7;
  color: #111;
  font-size: 1rem;
}
button {
  margin: .25rem;
  padding: .7rem 1rem;
  border: 0;
  border-radius: 12px;
  background: var(--accent);
  color: #161616;
  font-weight: 700;
  cursor: pointer;
}
button:hover { filter: brightness(1.08); }
.options { display: flex; flex-wrap: wrap; gap: .5rem; }
.feedback { min-height: 1.4rem; font-weight: 700; }
.ok { color: var(--ok); }
.bad { color: var(--bad); }
.locked { opacity: .38; pointer-events: none; filter: grayscale(.5); }
.sortable div {
  padding: .8rem 1rem;
  margin: .5rem 0;
  background: #0d1423;
  border: 1px solid var(--line);
  border-radius: 12px;
  cursor: grab;
}
.sortable div.dragging { opacity: .4; }
.testoutput { min-height: 70px; white-space: pre-wrap; }
.success {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: 14px;
  color: #08210f;
  background: #bdf5cf;
}
.hidden { display: none; }
.hint { color: var(--accent); }
footer { max-width: 980px; margin: 0 auto; padding: 1rem 1.5rem 2rem; color: var(--muted); }
@media (max-width: 700px) {
  header { position: static; flex-direction: column; align-items: flex-start; }
  .status { width: 100%; }
}