/* 
 * ChemMath StepEngine - High-Fidelity UI Stylesheet
 * Engineered with Photomath tokens and Telegram Mini App safe-area constraints
 */

:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  /* Photomath Core Tokens (Light Mode Default) */
  --pm-primary-red: #ea4335;
  --pm-primary-red-hover: #d93025;
  --pm-primary-red-light: #fef2f2;
  --pm-primary-red-border: #fecaca;
  --pm-accent-amber: #d97706;
  --pm-accent-amber-light: #fffbeb;
  --pm-accent-green: #10b981;
  --pm-accent-green-light: #ecfdf5;

  --pm-bg-main: #f8fafc;
  --pm-bg-card: #ffffff;
  --pm-bg-substep: #f1f5f9;
  --pm-bg-microstep: #ffffff;
  --pm-border: #e2e8f0;
  --pm-border-subtle: #edf2f7;

  --pm-text-primary: #0f172a;
  --pm-text-secondary: #64748b;
  --pm-text-muted: #94a3b8;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;

  /* Cubic-bezier from Photomath reverse deconstruction: fast_out_slow_in */
  --ease-fast-out-slow-in: cubic-bezier(0.2, 0.0, 0.2, 1.0);
}

/* Dark Mode Tokens */
body.dark-mode {
  --pm-primary-red: #ef4444;
  --pm-primary-red-hover: #dc2626;
  --pm-primary-red-light: #450a0a;
  --pm-primary-red-border: #7f1d1d;
  --pm-accent-amber: #f59e0b;
  --pm-accent-amber-light: #451a03;
  --pm-accent-green: #10b981;
  --pm-accent-green-light: #064e3b;

  --pm-bg-main: #0b1120;
  --pm-bg-card: #1e293b;
  --pm-bg-substep: #0f172a;
  --pm-bg-microstep: #1e293b;
  --pm-border: #334155;
  --pm-border-subtle: #1e293b;

  --pm-text-primary: #f8fafc;
  --pm-text-secondary: #94a3b8;
  --pm-text-muted: #64748b;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.4);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5);
}

/* Base Reset & Mobile Box Sizing */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--pm-bg-main);
  color: var(--pm-text-primary);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
  /* Safe-area clearance for Android TMA navigation bar */
  padding-bottom: calc(56px + env(safe-area-inset-bottom, 0px));
  padding-top: env(safe-area-inset-top, 0px);
}

.app-container {
  max-width: 680px;
  margin: 0 auto;
  padding: 12px 14px;
}

/* Header */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 4px 14px 4px;
  border-bottom: 1px solid var(--pm-border);
  margin-bottom: 14px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

.brand-icon {
  width: 38px;
  height: 38px;
  background: var(--pm-primary-red-light);
  color: var(--pm-primary-red);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--pm-primary-red-border);
}

.brand-title {
  font-size: 1.15rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 6px;
}

.badge-engine {
  background: var(--pm-primary-red);
  color: #ffffff;
  font-size: 0.68rem;
  font-weight: 700;
  padding: 2px 7px;
  border-radius: var(--radius-full);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.brand-subtitle {
  font-size: 0.72rem;
  color: var(--pm-text-secondary);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.btn-icon {
  width: 36px;
  height: 36px;
  background: var(--pm-bg-card);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-md);
  color: var(--pm-text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-icon:hover {
  background: var(--pm-border);
  color: var(--pm-text-primary);
}

/* Card Container */
.card {
  background: var(--pm-bg-card);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  padding: 16px;
  margin-bottom: 14px;
  transition: background-color 0.2s, border-color 0.2s;
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.card-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--pm-text-primary);
}

.user-badge {
  font-size: 0.75rem;
  padding: 2px 8px;
  background: var(--pm-bg-substep);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-full);
  color: var(--pm-text-secondary);
}

/* Problem Textarea */
.problem-textarea {
  width: 100%;
  border: 1.5px solid var(--pm-border);
  border-radius: var(--radius-md);
  padding: 12px;
  font-size: 0.95rem;
  font-family: inherit;
  background: var(--pm-bg-main);
  color: var(--pm-text-primary);
  resize: vertical;
  min-height: 84px;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.problem-textarea:focus {
  border-color: var(--pm-primary-red);
  box-shadow: 0 0 0 3px var(--pm-primary-red-light);
}

/* Scientific Keyboard Toolbar */
.scientific-toolbar {
  margin: 10px 0;
  padding: 8px 10px;
  background: var(--pm-bg-substep);
  border-radius: var(--radius-md);
  border: 1px solid var(--pm-border);
}

.toolbar-label {
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--pm-text-secondary);
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.toolbar-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
}

.tool-btn {
  background: var(--pm-bg-card);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-sm);
  padding: 4px 9px;
  font-size: 0.85rem;
  font-family: var(--font-mono);
  font-weight: 600;
  color: var(--pm-text-primary);
  cursor: pointer;
  touch-action: manipulation;
  transition: all 0.15s;
}

.tool-btn:hover, .tool-btn:active {
  background: var(--pm-primary-red-light);
  border-color: var(--pm-primary-red);
  color: var(--pm-primary-red);
  transform: translateY(-1px);
}

/* Presets */
.presets-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  margin: 10px 0;
}

.presets-label {
  font-size: 0.75rem;
  color: var(--pm-text-secondary);
  font-weight: 600;
}

.preset-pill {
  background: var(--pm-bg-substep);
  border: 1px dashed var(--pm-border);
  border-radius: var(--radius-full);
  padding: 3px 10px;
  font-size: 0.76rem;
  color: var(--pm-text-secondary);
  cursor: pointer;
  transition: all 0.15s;
}

.preset-pill:hover {
  background: var(--pm-bg-card);
  border-color: var(--pm-primary-red);
  color: var(--pm-primary-red);
}

/* Primary Solve Button */
.btn-primary-solve {
  width: 100%;
  padding: 13px 20px;
  background: var(--pm-primary-red);
  color: #ffffff;
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  box-shadow: 0 4px 12px rgba(234, 67, 53, 0.35);
  transition: all 0.2s var(--ease-fast-out-slow-in);
}

.btn-primary-solve:hover {
  background: var(--pm-primary-red-hover);
  transform: translateY(-1px);
}

.btn-primary-solve:active {
  transform: translateY(1px);
}

/* Implicit Context Banner */
.implicit-context-banner {
  background: var(--pm-accent-amber-light);
  border: 1px solid var(--pm-accent-amber);
  border-radius: var(--radius-md);
  padding: 10px 12px;
  display: flex;
  gap: 10px;
  align-items: flex-start;
  margin-bottom: 14px;
}

.banner-icon {
  font-size: 1.2rem;
}

.banner-title {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--pm-accent-amber);
  margin-bottom: 4px;
}

.implicit-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.implicit-tag {
  background: var(--pm-bg-card);
  border: 1px solid var(--pm-border);
  padding: 2px 8px;
  border-radius: var(--radius-full);
  font-size: 0.72rem;
  font-family: var(--font-mono);
  color: var(--pm-text-primary);
}

/* Alternative Method Switcher Tabs */
.methods-tabs-container {
  margin-bottom: 14px;
}

.methods-tabs-header {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--pm-text-secondary);
  margin-bottom: 8px;
}

.methods-tabs {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 8px;
}

.method-tab-card {
  background: var(--pm-bg-card);
  border: 1.5px solid var(--pm-border);
  border-radius: var(--radius-md);
  padding: 10px 12px;
  cursor: pointer;
  transition: all 0.2s var(--ease-fast-out-slow-in);
  position: relative;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.method-tab-card:hover {
  border-color: var(--pm-primary-red);
}

.method-tab-card.active {
  border-color: var(--pm-primary-red);
  background: var(--pm-primary-red-light);
  box-shadow: 0 0 0 1px var(--pm-primary-red);
}

.method-tab-title {
  font-size: 0.84rem;
  font-weight: 700;
  color: var(--pm-text-primary);
  margin-bottom: 2px;
}

.method-tab-subtitle {
  font-size: 0.72rem;
  color: var(--pm-text-secondary);
  line-height: 1.3;
}

.method-tab-footer {
  margin-top: 8px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.method-steps-count {
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--pm-primary-red);
}

.badge-recommended {
  background: var(--pm-accent-green);
  color: #ffffff;
  font-size: 0.65rem;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: var(--radius-full);
}

/* Final Answer Card */
.final-answer-card {
  border-left: 4px solid var(--pm-primary-red);
}

.final-answer-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 6px;
}

.status-indicator {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--pm-primary-red);
  display: inline-block;
}

.final-title {
  font-size: 0.95rem;
  font-weight: 700;
}

.final-answer-math {
  font-size: 1.05rem;
  padding: 6px 0;
  color: var(--pm-text-primary);
  overflow-x: auto;
}

/* Step Tree 3-Level Accordion */
.step-tree-container {
  margin-top: 14px;
}

.step-tree-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.tree-heading {
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--pm-text-primary);
}

.tree-controls {
  display: flex;
  gap: 6px;
}

.btn-ghost-sm {
  background: transparent;
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-sm);
  padding: 3px 8px;
  font-size: 0.74rem;
  color: var(--pm-text-secondary);
  cursor: pointer;
}

.btn-ghost-sm:hover {
  background: var(--pm-border);
  color: var(--pm-text-primary);
}

/* Level 1: Macro-Step Card */
.macro-step-card {
  background: var(--pm-bg-card);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-lg);
  margin-bottom: 12px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: all 0.24s var(--ease-fast-out-slow-in);
}

.macro-header {
  padding: 14px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  user-select: none;
  background: var(--pm-bg-card);
}

.macro-header:hover {
  background: var(--pm-bg-substep);
}

.macro-title-group {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 1;
}

.macro-number-badge {
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--pm-primary-red-light);
  color: var(--pm-primary-red);
  border: 1px solid var(--pm-primary-red-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 700;
}

.macro-title {
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--pm-text-primary);
}

.macro-indicator {
  display: flex;
  align-items: center;
  gap: 8px;
}

.substep-count-pill {
  font-size: 0.7rem;
  background: var(--pm-bg-substep);
  border: 1px solid var(--pm-border);
  padding: 2px 7px;
  border-radius: var(--radius-full);
  color: var(--pm-text-secondary);
}

.chevron-icon {
  width: 18px;
  height: 18px;
  color: var(--pm-text-secondary);
  transition: transform 0.24s var(--ease-fast-out-slow-in);
}

.macro-step-card.open .chevron-icon {
  transform: rotate(180deg);
}

.macro-summary-line {
  padding: 0 16px 12px 52px;
  font-size: 0.85rem;
  color: var(--pm-text-secondary);
  overflow-x: auto;
}

/* Macro Body (Accordion expansion) */
.macro-body {
  display: none;
  border-top: 1px solid var(--pm-border);
  background: var(--pm-bg-substep);
  padding: 12px 14px;
}

.macro-step-card.open .macro-body {
  display: block;
}

/* Level 2: Sub-Step Block */
.substep-block {
  background: var(--pm-bg-card);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-md);
  padding: 12px;
  margin-bottom: 10px;
}

.substep-block:last-child {
  margin-bottom: 0;
}

.substep-header {
  margin-bottom: 8px;
}

.substep-title {
  font-size: 0.86rem;
  font-weight: 700;
  color: var(--pm-text-primary);
}

.substep-rule {
  font-size: 0.75rem;
  color: var(--pm-accent-amber);
  margin-top: 2px;
}

/* Level 3: Micro-Step Item (Granular steps 30-50) */
.microstep-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.microstep-item {
  background: var(--pm-bg-substep);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-sm);
  padding: 8px 10px;
  transition: background-color 0.15s;
}

.microstep-item:hover {
  background: var(--pm-bg-card);
}

.microstep-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 4px;
}

.microstep-index {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--pm-primary-red);
}

.microstep-header {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--pm-text-primary);
  flex: 1;
  margin-left: 6px;
}

.microstep-math-flow {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding: 4px 0;
  font-size: 0.95rem;
  overflow-x: auto;
}

.diff-tag {
  display: inline-block;
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 600;
  font-family: var(--font-mono);
}

.diff-red {
  background: var(--pm-primary-red-light);
  color: var(--pm-primary-red);
  border: 1px solid var(--pm-primary-red-border);
}

.diff-amber {
  background: var(--pm-accent-amber-light);
  color: var(--pm-accent-amber);
  border: 1px solid #fde68a;
}

.diff-green {
  background: var(--pm-accent-green-light);
  color: var(--pm-accent-green);
  border: 1px solid #a7f3d0;
}

.microstep-explanation {
  font-size: 0.74rem;
  color: var(--pm-text-secondary);
  border-top: 1px dashed var(--pm-border);
  margin-top: 6px;
  padding-top: 4px;
}

/* Spinner */
.spinner {
  width: 18px;
  height: 18px;
  border: 2px solid rgba(255, 255, 255, 0.4);
  border-top-color: #ffffff;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  display: inline-block;
}

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

/* Admin Drawer */
.admin-drawer {
  position: fixed;
  inset: 0;
  z-index: 9999;
  display: flex;
  justify-content: flex-end;
}

.drawer-overlay {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(2px);
}

.drawer-content {
  position: relative;
  width: 85%;
  max-width: 420px;
  height: 100%;
  background: var(--pm-bg-card);
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  padding: 18px;
  overflow-y: auto;
}

.drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--pm-border);
  padding-bottom: 12px;
  margin-bottom: 14px;
}

.btn-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--pm-text-secondary);
}

.admin-metric-card {
  background: var(--pm-bg-substep);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-md);
  padding: 10px 12px;
  margin-bottom: 10px;
}

.metric-label {
  font-size: 0.75rem;
  color: var(--pm-text-secondary);
}

.metric-value {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--pm-text-primary);
  word-break: break-all;
}

.ast-dump {
  background: var(--pm-bg-substep);
  border: 1px solid var(--pm-border);
  border-radius: var(--radius-md);
  padding: 10px;
  font-size: 0.72rem;
  font-family: var(--font-mono);
  max-height: 280px;
  overflow: auto;
  white-space: pre-wrap;
}

/* Helpers */
.hidden {
  display: none !important;
}

.font-mono {
  font-family: var(--font-mono);
}