/* Decompose — the gym workout for physics thinking */

.decompose-page {
  min-height: 100vh;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
}

/* ---- Layout ---- */
.decompose-main {
  max-width: 52rem;
  margin: 0 auto;
  padding: var(--space-8) var(--space-6);
  position: relative;
}

/* ---- Header ---- */
.decompose-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) var(--space-6);
  border-bottom: 1px solid var(--color-divider);
  background: var(--color-surface);
}
.decompose-header .logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  text-decoration: none;
  color: var(--color-text);
}
.decompose-header .logo-text {
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.decompose-header .logo-dot {
  width: 8px;
  height: 8px;
  border-radius: var(--radius-full);
  background: var(--color-primary);
}
.decompose-back {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color var(--transition-interactive);
}
.decompose-back:hover { color: var(--color-primary); }

/* ============================================================
   INPUT SCREEN
   ============================================================ */
.dc-input-screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-6);
  padding: var(--space-16) 0 var(--space-12);
  text-align: center;
}
.dc-input-screen h1 {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 400;
  line-height: 1.2;
  max-width: 28rem;
}
.dc-input-screen p {
  color: var(--color-text-muted);
  font-size: var(--text-base);
  max-width: 30rem;
  line-height: 1.6;
}

.dc-input-wrap {
  width: 100%;
  max-width: 36rem;
  position: relative;
}
.dc-input-wrap textarea {
  width: 100%;
  min-height: 7rem;
  padding: var(--space-4);
  padding-bottom: var(--space-8);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: var(--color-surface);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  resize: vertical;
  transition: border-color var(--transition-interactive),
              box-shadow var(--transition-interactive);
}
.dc-input-wrap textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--color-primary) 15%, transparent);
}
.dc-input-wrap textarea::placeholder { color: var(--color-text-faint); }

.dc-input-hint {
  position: absolute;
  bottom: var(--space-3);
  right: var(--space-4);
  font-size: 0.7rem;
  color: var(--color-text-faint);
  pointer-events: none;
}

.dc-submit-btn {
  padding: var(--space-3) var(--space-10);
  border: none;
  border-radius: var(--radius-lg);
  background: var(--color-primary);
  color: #fff;
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.03em;
  cursor: pointer;
  transition: background var(--transition-interactive),
              transform var(--transition-interactive);
}
.dc-submit-btn:hover { background: var(--color-primary-hover); }
.dc-submit-btn:active { background: var(--color-primary-active); transform: scale(0.97); }
.dc-submit-btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }

.dc-examples {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  justify-content: center;
  max-width: 36rem;
}
.dc-example-btn {
  padding: var(--space-2) var(--space-4);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-full);
  background: transparent;
  color: var(--color-text-muted);
  font-family: var(--font-body);
  font-size: var(--text-xs);
  cursor: pointer;
  transition: all var(--transition-interactive);
}
.dc-example-btn:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: var(--color-primary-subtle);
}

/* ============================================================
   ANALYZING SCREEN
   ============================================================ */
.dc-analyzing {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-20) 0;
  text-align: center;
}
.dc-spinner {
  width: 36px;
  height: 36px;
  border: 3px solid var(--color-divider);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: dc-spin 0.8s linear infinite;
}
@keyframes dc-spin { to { transform: rotate(360deg); } }
.dc-analyzing-headline {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  color: var(--color-text);
}
.dc-analyzing-sub {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  max-width: 24rem;
  line-height: 1.5;
}

/* ============================================================
   WORKOUT SCREEN
   ============================================================ */
.dc-workout {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.dc-original-problem {
  padding: var(--space-4) var(--space-5);
  border-left: 3px solid var(--color-primary);
  background: var(--color-primary-subtle);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-size: var(--text-sm);
  line-height: 1.6;
}
.dc-original-problem .dc-label {
  display: block;
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-primary);
  margin-bottom: var(--space-1);
}

/* ---- Progress ---- */
.dc-progress {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}
.dc-progress-steps {
  display: flex;
  gap: var(--space-2);
  flex: 1;
}
.dc-progress-step {
  flex: 1;
  height: 5px;
  border-radius: var(--radius-full);
  background: var(--color-divider);
  transition: background 0.5s ease;
}
.dc-progress-step.done { background: var(--color-success); }
.dc-progress-step.active {
  background: var(--color-primary);
  animation: dc-pulse 2s ease-in-out infinite;
}
@keyframes dc-pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}
.dc-progress-label {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-text-muted);
  white-space: nowrap;
}

/* ---- Sub-problem card ---- */
.dc-subproblem {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  background: var(--color-surface);
  overflow: hidden;
  transition: border-color var(--transition-interactive),
              opacity var(--transition-interactive),
              box-shadow var(--transition-interactive);
}
.dc-subproblem.locked {
  opacity: 0.45;
  pointer-events: none;
}
.dc-subproblem.active {
  border-color: var(--color-primary);
  box-shadow: 0 2px 16px color-mix(in srgb, var(--color-primary) 12%, transparent);
  opacity: 1;
}
.dc-subproblem.done {
  border-color: var(--color-success);
  opacity: 0.6;
}

.dc-subproblem-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  padding: var(--space-5);
}

.dc-step-badge {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  border-radius: var(--radius-full);
  background: var(--color-surface-offset);
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  font-weight: 700;
  flex-shrink: 0;
  transition: all var(--transition-interactive);
}
.dc-subproblem.active .dc-step-badge {
  background: var(--color-primary);
  color: #fff;
}
.dc-subproblem.done .dc-step-badge {
  background: var(--color-success);
  color: #fff;
}

.dc-subproblem-info { flex: 1; min-width: 0; }

.dc-gap-label {
  display: inline-block;
  padding: 2px var(--space-3);
  border-radius: var(--radius-full);
  background: var(--color-primary-subtle);
  color: var(--color-primary);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  margin-bottom: var(--space-2);
}
.dc-gap-reason {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin: 0 0 var(--space-2);
  line-height: 1.4;
  font-style: italic;
}
.dc-subproblem-text {
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-text);
  margin: 0;
}

/* ---- Chat area ---- */
.dc-chat-area {
  border-top: 1px solid var(--color-divider);
  display: none;
}
.dc-subproblem.active .dc-chat-area {
  display: block;
}

.dc-messages {
  padding: var(--space-4) var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  min-height: 100px;
  max-height: 400px;
  overflow-y: auto;
  scroll-behavior: smooth;
}

.dc-msg {
  max-width: 85%;
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-lg);
  font-size: var(--text-sm);
  line-height: 1.6;
  word-break: break-word;
}
.dc-msg p { margin: 0 0 0.4em; }
.dc-msg p:last-child { margin-bottom: 0; }
.dc-msg ul, .dc-msg ol { margin: 0.3em 0; padding-left: 1.4em; }

.dc-msg.user {
  align-self: flex-end;
  background: var(--color-user-bubble);
  color: var(--color-user-text);
  border-bottom-right-radius: var(--radius-sm);
}
.dc-msg.assistant {
  align-self: flex-start;
  background: var(--color-surface-offset);
  color: var(--color-text);
  border-bottom-left-radius: var(--radius-sm);
}

/* Typing dots */
.dc-typing {
  display: flex;
  gap: 4px;
  padding: var(--space-3) var(--space-4);
}
.dc-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-text-faint);
  animation: dc-bounce 1.4s ease-in-out infinite;
}
.dc-dot:nth-child(2) { animation-delay: 0.2s; }
.dc-dot:nth-child(3) { animation-delay: 0.4s; }
@keyframes dc-bounce {
  0%, 80%, 100% { transform: scale(0.7); opacity: 0.4; }
  40% { transform: scale(1); opacity: 1; }
}

/* Chat input row */
.dc-chat-input-row {
  display: flex;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
}
.dc-chat-input {
  flex: 1;
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  transition: border-color var(--transition-interactive);
}
.dc-chat-input:focus {
  outline: none;
  border-color: var(--color-primary);
}
.dc-chat-send {
  padding: var(--space-3) var(--space-5);
  border: none;
  border-radius: var(--radius-lg);
  background: var(--color-primary);
  color: #fff;
  font-size: var(--text-sm);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition-interactive);
}
.dc-chat-send:hover { background: var(--color-primary-hover); }
.dc-chat-send:disabled { opacity: 0.35; cursor: not-allowed; }

/* Done button */
.dc-done-btn {
  display: block;
  margin: 0 var(--space-5) var(--space-5);
  padding: var(--space-3);
  width: calc(100% - var(--space-10));
  border: 1.5px dashed var(--color-success);
  border-radius: var(--radius-lg);
  background: transparent;
  color: var(--color-success);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-interactive);
}
.dc-done-btn:hover {
  background: var(--color-success-highlight);
  border-style: solid;
}

/* ============================================================
   RETURN SCREEN
   ============================================================ */
.dc-return {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-6);
  padding: var(--space-12) 0;
  text-align: center;
}
.dc-return-icon {
  width: 3.5rem;
  height: 3.5rem;
  border-radius: var(--radius-full);
  background: var(--color-success);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 700;
}
.dc-return h2 {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 400;
  max-width: 24rem;
}
.dc-return-prompt {
  max-width: 32rem;
  padding: var(--space-5);
  border-radius: var(--radius-lg);
  background: var(--color-primary-subtle);
  font-size: var(--text-sm);
  line-height: 1.6;
  text-align: left;
}
.dc-return-original {
  max-width: 32rem;
  width: 100%;
  text-align: left;
}
.dc-return-actions {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
  justify-content: center;
}
.dc-action-btn {
  padding: var(--space-3) var(--space-6);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: transparent;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition-interactive);
}
.dc-action-btn:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}
.dc-action-primary {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}
.dc-action-primary:hover {
  background: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  color: #fff;
}

/* ============================================================
   REATTEMPT
   ============================================================ */
.dc-reattempt {
  width: 100%;
  max-width: 36rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  background: var(--color-surface);
  overflow: hidden;
}
.dc-reattempt-messages {
  padding: var(--space-4) var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  min-height: 80px;
  max-height: 400px;
  overflow-y: auto;
  scroll-behavior: smooth;
}
.dc-reattempt .dc-chat-input-row {
  border-top: 1px solid var(--color-divider);
}

/* ============================================================
   TOAST
   ============================================================ */
.dc-toast {
  position: fixed;
  bottom: var(--space-6);
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-lg);
  background: var(--color-error);
  color: #fff;
  font-size: var(--text-sm);
  box-shadow: var(--shadow-lg);
  z-index: 100;
  animation: dc-slide-up 0.3s ease;
}
@keyframes dc-slide-up {
  from { transform: translateX(-50%) translateY(1rem); opacity: 0; }
  to   { transform: translateX(-50%) translateY(0);    opacity: 1; }
}
.dc-toast-close {
  background: none;
  border: none;
  color: inherit;
  font-size: 1.2rem;
  cursor: pointer;
  padding: 0;
  line-height: 1;
  opacity: 0.7;
}
.dc-toast-close:hover { opacity: 1; }

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

/* ============================================================
   MOBILE
   ============================================================ */
@media (max-width: 640px) {
  .decompose-main { padding: var(--space-4) var(--space-4); }
  .dc-input-screen { padding: var(--space-10) 0 var(--space-8); }
  .dc-input-screen h1 { font-size: var(--text-lg); }
  .dc-subproblem-header { padding: var(--space-4); }
  .dc-messages { padding: var(--space-3) var(--space-4); max-height: 300px; }
  .dc-chat-input-row { padding: var(--space-2) var(--space-4); }
  .dc-done-btn { margin: 0 var(--space-4) var(--space-4); width: calc(100% - var(--space-8)); }
  .dc-return-actions { flex-direction: column; align-items: center; }
}