:root {
  --practice-green: #61e3a5;
  --practice-blue: #6bbcff;
  --practice-yellow: #ffd166;
  --practice-red: #ff8585;
  --practice-surface: #101a1f;
  --practice-line: #293b44;
}

.exercises-hero {
  background: radial-gradient(circle at 88% 12%, rgba(107, 188, 255, .12), transparent 32%), rgba(12, 22, 26, .96);
}

.practice-summary {
  display: grid;
  margin: 1.5rem 0;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: .75rem;
}

.practice-summary article {
  display: flex;
  min-height: 86px;
  padding: 1rem;
  align-items: center;
  gap: .8rem;
  border: 1px solid var(--practice-line);
  border-radius: 11px;
  background: rgba(255, 255, 255, .025);
}

.practice-summary strong {
  color: var(--practice-green);
  font: 700 1.35rem ui-monospace, monospace;
}

.practice-summary span { color: #a8b6bc; font-size: .84rem; }

.progress-panel {
  display: grid;
  padding: 1rem;
  grid-template-columns: 190px minmax(180px, 1fr) auto;
  align-items: center;
  gap: 1rem;
  border: 1px solid rgba(97, 227, 165, .3);
  border-radius: 12px;
  background: rgba(97, 227, 165, .045);
}

.progress-panel > div:first-child span,
.progress-panel > div:first-child strong { display: block; }
.progress-panel > div:first-child span { color: #7f9199; font-size: .7rem; text-transform: uppercase; }
.progress-panel > div:first-child strong { color: #f1f5f9; font-size: .9rem; }
.progress-track { height: 9px; overflow: hidden; border-radius: 999px; background: #071014; }
.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--practice-green), var(--practice-blue));
  transition: width .35s ease;
}

#reset-progress,
.exercise-filters button,
.check-quiz {
  border: 1px solid #3b505a;
  border-radius: 7px;
  color: #cbd5e1;
  background: #132027;
  cursor: pointer;
  font-weight: 700;
}

#reset-progress { padding: .62rem .75rem; }
#reset-progress i, .check-quiz i { margin-right: .4rem; }

.study-cycle {
  display: grid;
  margin-top: 1.4rem;
  grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr;
  align-items: center;
  gap: .65rem;
}

.study-cycle article {
  display: grid;
  min-height: 118px;
  padding: 1rem;
  grid-template-columns: 34px 1fr;
  gap: .7rem;
  border: 1px solid var(--practice-line);
  border-radius: 10px;
  background: var(--practice-surface);
}

.study-cycle article > span {
  display: grid;
  width: 32px;
  height: 32px;
  place-items: center;
  border: 1px solid rgba(97, 227, 165, .45);
  border-radius: 8px;
  color: var(--practice-green);
  font: 700 .75rem ui-monospace, monospace;
}

.study-cycle strong { color: #f1f5f9; }
.study-cycle p { margin: .25rem 0 0; color: #8799a2; font-size: .78rem; line-height: 1.45; }
.study-cycle > i { color: var(--practice-yellow); }
.practice-rule {
  display: flex;
  margin-top: 1rem;
  padding: .9rem 1rem;
  gap: .8rem;
  border-left: 3px solid var(--practice-blue);
  background: rgba(107, 188, 255, .055);
}
.practice-rule i { margin-top: .25rem; color: var(--practice-blue); }
.practice-rule p { margin: 0; color: #b6c3c8; }

.exercise-filters {
  display: flex;
  position: sticky;
  z-index: 4;
  top: 86px;
  margin: 1rem 0 1.2rem;
  padding: .7rem;
  flex-wrap: wrap;
  gap: .5rem;
  border: 1px solid var(--practice-line);
  border-radius: 10px;
  background: rgba(9, 17, 21, .95);
  backdrop-filter: blur(12px);
}

.exercise-filters button { padding: .55rem .8rem; font-size: .75rem; }
.exercise-filters button:hover,
.exercise-filters button.is-active {
  border-color: var(--practice-green);
  color: #07110c;
  background: var(--practice-green);
}

.exercise-list { display: grid; min-width: 0; gap: 1rem; }
.exercise-card {
  min-width: 0;
  padding: clamp(1rem, 2.5vw, 1.45rem);
  overflow: hidden;
  border: 1px solid var(--practice-line);
  border-radius: 14px;
  background: linear-gradient(135deg, rgba(255,255,255,.018), transparent 45%), #0e181d;
}
.exercise-card[hidden] { display: none; }
.exercise-card.is-done { border-color: rgba(97, 227, 165, .5); box-shadow: inset 4px 0 0 rgba(97, 227, 165, .7); }
.exercise-topline { display: flex; align-items: center; flex-wrap: wrap; gap: .5rem; }
.exercise-number {
  display: grid;
  width: 34px;
  height: 34px;
  place-items: center;
  border: 1px solid rgba(107, 188, 255, .45);
  border-radius: 8px;
  color: var(--practice-blue);
  font: 700 .7rem ui-monospace, monospace;
}
.difficulty, .topic { padding: .27rem .5rem; border-radius: 999px; font: 600 .62rem ui-monospace, monospace; }
.difficulty.easy { color: var(--practice-green); background: rgba(97,227,165,.09); }
.difficulty.medium { color: var(--practice-yellow); background: rgba(255,209,102,.09); }
.difficulty.hard { color: var(--practice-red); background: rgba(255,133,133,.09); }
.topic { color: #a8b6bc; border: 1px solid #30434c; }
.done-control { margin-left: auto; cursor: pointer; }
.done-control input { position: absolute; opacity: 0; pointer-events: none; }
.done-control span {
  display: inline-flex;
  padding: .42rem .65rem;
  align-items: center;
  gap: .38rem;
  border: 1px solid #354a54;
  border-radius: 7px;
  color: #8fa0a8;
  font-size: .72rem;
}
.done-control input:focus-visible + span { outline: 3px solid rgba(107,188,255,.35); }
.done-control input:checked + span { border-color: var(--practice-green); color: #07110c; background: var(--practice-green); }
.exercise-card h3 { margin: .9rem 0 .4rem; color: #f1f5f9; font-size: clamp(1.2rem, 2.4vw, 1.65rem); }
.exercise-context { max-width: 970px; color: #a8b6bc; }
.exercise-objectives { display: flex; margin: 1rem 0; align-items: center; flex-wrap: wrap; gap: .45rem; }
.exercise-objectives strong { margin-right: .3rem; color: #e2e8f0; font-size: .75rem; }
.exercise-objectives span { padding: .3rem .48rem; border: 1px solid #2e424c; border-radius: 6px; background: #091216; }

.io-grid { display: grid; min-width: 0; margin: 1rem 0; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: .7rem; }
.io-grid > div { min-width: 0; overflow: hidden; border: 1px solid var(--practice-line); border-radius: 9px; background: #081115; }
.io-grid small { display: block; padding: .5rem .75rem; color: var(--practice-green); border-bottom: 1px solid var(--practice-line); font: 600 .65rem ui-monospace, monospace; text-transform: uppercase; }
.io-grid pre { margin: 0; padding: .8rem; overflow-x: auto; color: #d8e2e6; font-size: .78rem; }

.hint, .solution { margin-top: .7rem; border: 1px solid var(--practice-line); border-radius: 9px; background: #0a1418; }
.hint summary, .solution summary { padding: .75rem .9rem; color: #c6d1d5; cursor: pointer; font-weight: 700; list-style: none; }
.hint summary::-webkit-details-marker, .solution summary::-webkit-details-marker { display: none; }
.hint summary i { margin-right: .5rem; color: var(--practice-yellow); }
.solution summary i { margin-right: .5rem; color: var(--practice-blue); }
.hint p { margin: 0; padding: 0 .9rem .9rem; color: #9aabb2; }
.solution-body { padding: 0 .9rem .9rem; }
.solution-code { position: relative; margin: 0; overflow: auto; border: 1px solid #22343d; border-radius: 8px; background: #050b0e; }
.solution-code code { display: block; min-width: max-content; padding: 1rem; color: #d8e4e8; font: .78rem/1.65 ui-monospace, SFMono-Regular, Consolas, monospace; background: transparent; border: 0; }
.solution-code code.hljs { color: #abb2bf; background: transparent; }
.solution-code .hljs-keyword, .solution-code .hljs-selector-tag, .solution-code .hljs-literal { color: #c678dd; }
.solution-code .hljs-type, .solution-code .hljs-built_in { color: #e5c07b; }
.solution-code .hljs-title.function_, .solution-code .hljs-function .hljs-title { color: #61afef; }
.solution-code .hljs-string { color: #98c379; }
.solution-code .hljs-number { color: #d19a66; }
.solution-code .hljs-comment { color: #7f8c98; font-style: italic; }
.solution-code .hljs-meta { color: #56b6c2; }
.solution-code .hljs-params, .solution-code .hljs-variable { color: #e06c75; }
.copy-code { position: absolute; top: .55rem; right: .55rem; padding: .38rem .55rem; border: 1px solid #36505c; border-radius: 6px; color: #aebcc2; background: rgba(13,25,31,.94); cursor: pointer; font-size: .68rem; }
.copy-code:hover { color: var(--practice-green); border-color: var(--practice-green); }
.solution-note { margin: .75rem 0 0; padding: .75rem; color: #9babb2; border-left: 3px solid var(--practice-green); background: rgba(97,227,165,.04); }
.solution-note strong { color: #e2e8f0; }

.before-after, .contract-board, .linear-diagram, .memory-diagram, .linked-diagram {
  display: flex;
  margin: 1rem 0;
  padding: 1rem;
  align-items: center;
  justify-content: center;
  gap: .8rem;
  overflow-x: auto;
  border: 1px solid var(--practice-line);
  border-radius: 10px;
  background: #091216;
}
.before-after > div, .contract-board > div { display: grid; min-width: 0; gap: .25rem; }
.before-after small, .contract-board small { color: #73858e; font-size: .62rem; text-transform: uppercase; }
.before-after > i, .contract-board > i { color: var(--practice-yellow); }
.linear-diagram span, .linked-diagram span {
  padding: .55rem .7rem;
  border: 1px solid rgba(107,188,255,.55);
  border-radius: 7px;
  color: #e2e8f0;
  background: rgba(107,188,255,.07);
}
.linear-diagram i, .linked-diagram i { color: var(--practice-green); }
.linked-diagram { justify-content: flex-start; }
.linked-diagram b { color: var(--practice-yellow); }
.linked-diagram small { color: #83969f; }
.memory-diagram > div { display: grid; padding: .7rem 1rem; border: 1px solid var(--practice-blue); border-radius: 8px; }
.memory-diagram small { color: #81959e; }
.memory-diagram > span { display: grid; place-items: center; color: var(--practice-green); }

.record-diagram {
  display: flex;
  margin: 1rem 0;
  padding: 1rem;
  overflow-x: auto;
  align-items: stretch;
  gap: .6rem;
  border: 1px solid var(--practice-line);
  border-radius: 10px;
  background: #091216;
}
.record-diagram > span { display: grid; min-width: 120px; place-items: center; color: var(--practice-yellow); font: 700 .72rem ui-monospace, monospace; }
.record-diagram > div { display: grid; min-width: 130px; padding: .6rem; gap: .2rem; border: 1px solid #3c5662; border-radius: 7px; background: #13252d; }
.record-diagram small, .record-diagram em { color: #80939c; font-style: normal; }

.complexity-quiz { display: grid; margin: 1rem 0; grid-template-columns: 1fr 1fr; gap: .7rem; }
.complexity-quiz article { display: grid; padding: .8rem; grid-template-columns: 30px minmax(0,1fr); gap: .6rem; border: 1px solid var(--practice-line); border-radius: 9px; background: #091216; }
.complexity-quiz article > b { display: grid; width: 28px; height: 28px; place-items: center; border-radius: 7px; color: #07110c; background: var(--practice-blue); }
.complexity-quiz pre { grid-column: 2; margin: 0; overflow-x: auto; color: #d8e2e6; font-size: .73rem; }
.complexity-quiz select { grid-column: 2; padding: .5rem; border: 1px solid #38505b; border-radius: 6px; color: #d5e0e4; background: #111e24; }
.complexity-quiz select.is-correct { border-color: var(--practice-green); }
.complexity-quiz select.is-wrong { border-color: var(--practice-red); }
.check-quiz { padding: .6rem .8rem; }
.quiz-feedback { display: inline-block; margin: 0 0 0 .7rem; color: #a8b6bc; }
.answer-grid { display: grid; grid-template-columns: 1fr 1fr; gap: .6rem; }
.answer-grid span { padding: .75rem; color: #96a8b0; border: 1px solid var(--practice-line); border-radius: 7px; }
.answer-grid strong { display: block; color: var(--practice-green); }

.binary-diagram { display: grid; margin: 1rem 0; grid-template-columns: repeat(7, 1fr); overflow-x: auto; }
.binary-diagram span { position: relative; display: grid; min-width: 75px; min-height: 58px; place-items: center; border: 1px solid #3b5561; border-right: 0; color: #e2e8f0; background: #091216; font: .8rem ui-monospace, monospace; }
.binary-diagram span:last-child { border-right: 1px solid #3b5561; }
.binary-diagram span.middle { color: #07110c; background: var(--practice-yellow); }
.binary-diagram span small { position: absolute; top: 2px; color: #6b4d00; font-size: .55rem; }

.graph-challenge-layout { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(280px, .9fr); gap: 1rem; }
.challenge-graph, .challenge-copy { padding: 1rem; border: 1px solid var(--practice-line); border-radius: 11px; background: #091216; }
.challenge-graph svg { display: block; width: 100%; height: auto; }
.challenge-graph .edges { stroke: #55727d; stroke-width: 3; }
.challenge-graph circle { fill: #123225; stroke: var(--practice-green); stroke-width: 3; }
.challenge-graph text { fill: #f1f5f9; text-anchor: middle; font: 700 16px system-ui; }
.challenge-copy h3 { color: #f1f5f9; }
.challenge-copy li { margin-bottom: .55rem; color: #a8b6bc; }
.challenge-copy p { color: #8799a2; }

@media (max-width: 900px) {
  .progress-panel { grid-template-columns: 1fr; }
  .study-cycle { grid-template-columns: 1fr; }
  .study-cycle > i { transform: rotate(90deg); justify-self: center; }
  .graph-challenge-layout { grid-template-columns: 1fr; }
  .exercise-filters { top: 72px; }
}

@media (max-width: 680px) {
  .practice-summary, .io-grid, .complexity-quiz, .answer-grid { grid-template-columns: minmax(0, 1fr); }
  .done-control { width: 100%; margin: .25rem 0 0; }
  .done-control span { justify-content: center; width: 100%; }
  .before-after, .contract-board { flex-direction: column; align-items: stretch; }
  .before-after > i { transform: rotate(90deg); align-self: center; }
  .contract-board > i { align-self: center; }
  .exercise-filters { position: static; }
  .memory-diagram { flex-wrap: wrap; }
}

@media (prefers-reduced-motion: reduce) {
  .progress-track span { transition: none; }
}