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

:root {
  --bg: #0f1117;
  --surface: #1a1d27;
  --surface2: #242736;
  --border: #2e3248;
  --text: #e4e6f0;
  --text-dim: #8b8fa8;
  --accent: #6c8cff;
  --accent-hover: #8ba4ff;
  --green: #4cdf8b;
  --orange: #ffb347;
  --red: #ff6b6b;
  --hint-bg: #1e2a3a;
  --answer-bg: #1a2e1a;
}

body {
  font-family: 'Segoe UI', 'Hiragino Sans', 'Noto Sans JP', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

header {
  padding: 16px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 24px;
  flex-wrap: wrap;
}

header h1 {
  font-size: 1.3rem;
  white-space: nowrap;
}

.home-link {
  font-size: 1.5rem;
  color: var(--text-dim);
  text-decoration: none;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 6px;
  transition: all 0.2s;
}

.home-link:hover {
  background: var(--surface2);
  color: var(--accent);
}

#category-nav {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.cat-btn {
  padding: 8px 20px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface2);
  color: var(--text-dim);
  cursor: pointer;
  font-size: 0.9rem;
  transition: all 0.2s;
}

.cat-btn:hover { border-color: var(--accent); color: var(--text); }
.cat-btn.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.progress-bar-container {
  height: 28px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: relative;
  display: flex;
  align-items: center;
  padding: 0 24px;
}

.progress-bar {
  position: absolute;
  left: 0; top: 0; bottom: 0;
  background: linear-gradient(90deg, var(--accent), var(--green));
  opacity: 0.2;
  transition: width 0.4s;
  width: 0%;
}

#progress-text {
  position: relative;
  font-size: 0.8rem;
  color: var(--text-dim);
}

main {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  height: calc(100vh - 94px);
}

#problem-panel, #editor-panel {
  padding: 24px;
  overflow-y: auto;
}

#problem-panel {
  border-right: 1px solid var(--border);
}

.panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}

.panel-header h2 { font-size: 1.1rem; }

.badge {
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 0.75rem;
  font-weight: 600;
}

.badge.basic { background: var(--green); color: #111; }
.badge.intermediate { background: var(--orange); color: #111; }
.badge.advanced { background: var(--red); color: #fff; }

.tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

.tags span {
  padding: 2px 8px;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 4px;
  font-size: 0.7rem;
  color: var(--text-dim);
}

#problem-description {
  font-size: 1rem;
  line-height: 1.8;
  margin-bottom: 16px;
  white-space: pre-wrap;
}

.expected-output {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px;
  margin-bottom: 16px;
}

.expected-output h4 { font-size: 0.85rem; color: var(--text-dim); margin-bottom: 8px; }
.expected-output pre {
  font-family: 'Fira Code', 'Consolas', monospace;
  font-size: 0.85rem;
  color: var(--green);
}

.btn-group {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.primary-btn {
  padding: 10px 24px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.9rem;
  transition: background 0.2s;
}

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

.secondary-btn {
  padding: 8px 16px;
  background: var(--surface2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
  transition: all 0.2s;
}

.secondary-btn:hover { border-color: var(--accent); }

.secondary-btn.small {
  padding: 4px 10px;
  font-size: 0.75rem;
  color: var(--red);
  border-color: transparent;
}
.secondary-btn.small:hover { border-color: var(--red); }

.info-box {
  border-radius: 8px;
  padding: 16px;
  margin-bottom: 16px;
  animation: fadeIn 0.3s;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: translateY(0); }
}

.hint-box {
  background: var(--hint-bg);
  border: 1px solid #2a4a6a;
}

.hint-box h4 { color: var(--orange); margin-bottom: 8px; }

.answer-box {
  background: var(--answer-bg);
  border: 1px solid #2a5a2a;
}

.answer-box h4 { color: var(--green); margin-bottom: 8px; }

.answer-box pre {
  font-family: 'Fira Code', 'Consolas', monospace;
  font-size: 0.9rem;
  background: #111;
  padding: 12px;
  border-radius: 6px;
  overflow-x: auto;
  margin-bottom: 8px;
}

#answer-explanation {
  font-size: 0.85rem;
  color: var(--text-dim);
  line-height: 1.6;
}

.nav-buttons {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-top: 24px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
}

.nav-btn {
  padding: 8px 16px;
  background: var(--surface2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
}

.nav-btn:disabled { opacity: 0.4; cursor: not-allowed; }
.nav-btn:not(:disabled):hover { border-color: var(--accent); }

#question-select {
  flex: 1;
  padding: 8px;
  background: var(--surface2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.85rem;
}

#code-editor {
  width: 100%;
  height: calc(100% - 160px);
  min-height: 300px;
  background: #111318;
  color: #e4e6f0;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  font-family: 'Fira Code', 'Consolas', 'Courier New', monospace;
  font-size: 0.95rem;
  line-height: 1.6;
  resize: none;
  tab-size: 2;
}

#code-editor:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 2px rgba(108, 140, 255, 0.2);
}

.editor-actions {
  display: flex;
  gap: 6px;
}

.icon-btn {
  width: 32px;
  height: 32px;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text-dim);
  cursor: pointer;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.icon-btn:hover { border-color: var(--accent); color: var(--text); }

.editor-footer {
  display: flex;
  gap: 12px;
  margin-top: 12px;
  margin-bottom: 12px;
  align-items: center;
}

/* Mastery system */
.mastery-group {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
}

.mastery-label {
  font-size: 0.8rem;
  color: var(--text-dim);
  margin-right: 4px;
}

.mastery-btn {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: var(--surface2);
  color: var(--text-dim);
  font-size: 0.8rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.mastery-btn:hover {
  border-color: var(--accent);
  color: var(--text);
}

.mastery-btn.mastery-reset {
  width: 28px;
  height: 28px;
  font-size: 0.7rem;
  margin-left: 4px;
  border-radius: 6px;
}

.mastery-btn.active[data-level="1"] {
  background: #2a3a1a;
  border-color: #7ab648;
  color: #7ab648;
}

.mastery-btn.active[data-level="2"] {
  background: #1a3a2a;
  border-color: #4cdf8b;
  color: #4cdf8b;
}

.mastery-btn.active[data-level="3"] {
  background: #1a2a4a;
  border-color: #6cb4ff;
  color: #6cb4ff;
  box-shadow: 0 0 8px rgba(108, 180, 255, 0.3);
}

.mastery-display {
  font-size: 0.82rem;
  color: var(--text-dim);
  margin-bottom: 10px;
  min-height: 20px;
}

#result-box.correct {
  background: var(--answer-bg);
  border: 1px solid var(--green);
}

#result-box.incorrect {
  background: #2e1a1a;
  border: 1px solid var(--red);
}

#result-box.correct #result-content { color: var(--green); }
#result-box.incorrect #result-content { color: var(--red); }

/* Shortcut capture area */
#shortcut-capture-area {
  width: 100%;
  min-height: 300px;
  background: #111318;
  border: 2px dashed var(--border);
  border-radius: 12px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 24px;
  cursor: pointer;
  transition: all 0.3s;
  outline: none;
  user-select: none;
}

#shortcut-capture-area:focus {
  border-color: var(--accent);
  border-style: solid;
  box-shadow: 0 0 0 3px rgba(108, 140, 255, 0.25);
}

#shortcut-capture-area:focus .shortcut-prompt {
  color: var(--accent);
}

.shortcut-prompt {
  font-size: 1rem;
  color: var(--text-dim);
  transition: color 0.2s;
}

.shortcut-keys-display {
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
  justify-content: center;
  min-height: 60px;
}

.shortcut-key {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 52px;
  height: 52px;
  padding: 0 16px;
  background: var(--surface2);
  border: 2px solid var(--border);
  border-radius: 8px;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
  box-shadow: 0 3px 0 #1a1d27;
  transition: all 0.15s;
}

.shortcut-key.active {
  background: var(--accent);
  border-color: var(--accent-hover);
  color: #fff;
  box-shadow: 0 1px 0 #4a6adf;
  transform: translateY(2px);
}

.shortcut-key-plus {
  font-size: 1.2rem;
  color: var(--text-dim);
  font-weight: 700;
}

.shortcut-input-text {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text);
  min-height: 32px;
}

.shortcut-result-correct .shortcut-key {
  background: #1a3a2a;
  border-color: var(--green);
  color: var(--green);
}

.shortcut-result-incorrect .shortcut-key {
  background: #3a1a1a;
  border-color: var(--red);
  color: var(--red);
}

/* Question select done marker */
.done-option { }

@media (max-width: 900px) {
  main {
    grid-template-columns: 1fr;
    height: auto;
  }
  #problem-panel { border-right: none; border-bottom: 1px solid var(--border); }
  #code-editor { min-height: 200px; height: 300px; }
}