/* ===== About Page — Theme ===== */

/* --- Page wrapper --- */
/* Sections handle their own max-widths,
   allowing full-bleed background alternation. */

/* Shared heading style — typography-driven hierarchy, no emoji clutter.
   Uses serif for warmth, generous bottom margin for breathing room. */
.about-heading {
  font-family: var(--font-serif);
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-6);
  letter-spacing: 0.01em;
}

/* Shared inner column — constrains content width for comfortable reading
   (≈ 30 Chinese chars per line at 0.95rem body text). */
.about-inner-col {
  max-width: 620px;
  margin: 0 auto;
  padding-left: var(--space-6);
  padding-right: var(--space-6);
}

/* ===================================================
   HERO — Full-width warm background, generous padding.
   Acts as both intro + mission. Merges the old "这是什么"
   section to avoid repetition.
   =================================================== */
.about-hero {
  text-align: center;
  padding: 120px var(--space-6) var(--space-16);
  background: linear-gradient(
    170deg,
    rgba(122, 107, 191, 0.05) 0%,
    rgba(130, 180, 150, 0.04) 100%
  );
}

.about-hero-inner {
  max-width: 540px;
  margin: 0 auto;
}

.about-hero-eyebrow {
  font-size: 0.8rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-primary);
  margin-bottom: var(--space-4);
}

.about-hero-title {
  font-family: var(--font-serif);
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-text);
  line-height: 1.3;
  margin-bottom: var(--space-5);
}

.about-hero-body {
  font-size: 1rem;
  color: var(--color-text-secondary);
  line-height: 1.8;
  margin-bottom: var(--space-5);
}

.about-hero-mission {
  font-size: 0.95rem;
  color: var(--color-text);
  font-weight: 500;
  line-height: 1.75;
  /* Subtle left accent to lift the mission statement */
  border-left: 3px solid var(--color-primary-light);
  padding-left: var(--space-4);
  text-align: left;
  max-width: 440px;
  margin: 0 auto;
}

/* ===================================================
   CONTENTS GRID — Three columns on desktop, stacked
   on mobile. Cards use spacing + icon size for hierarchy,
   no borders (Refactoring UI: "Borders aren't the only
   way to make elements feel distinct.").
   =================================================== */
.about-contents {
  max-width: 720px;
  margin: 0 auto;
  padding: var(--space-16) var(--space-6);
}



.about-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-6);
}

.about-grid-item {
  text-align: center;
  padding: var(--space-6) var(--space-4);
}

.about-grid-icon {
  font-size: 2rem;
  display: block;
  margin-bottom: var(--space-3);
}

.about-grid-name {
  font-weight: 600;
  font-size: 1rem;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.about-grid-desc {
  font-size: 0.88rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

/* ===================================================
   HOW TO USE — PWA install guide. Two-column intro
   cards + numbered step list. Calm, instructional tone.
   =================================================== */
.about-howto {
  max-width: 620px;
  margin: 0 auto;
  padding: var(--space-16) var(--space-6) var(--space-10);
}

.about-howto-intro {
  margin-bottom: var(--space-8);
}

.about-howto-intro p {
  font-size: 0.93rem;
  color: var(--color-text-secondary);
  line-height: 1.8;
}

.about-howto-intro strong {
  color: var(--color-text);
  font-weight: 600;
}

.about-howto-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin-bottom: var(--space-8);
}

.about-howto-card {
  text-align: center;
  padding: var(--space-5) var(--space-4);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
}

.about-howto-icon {
  font-size: 1.6rem;
  display: block;
  margin-bottom: var(--space-3);
}

.about-howto-card-title {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.about-howto-card-desc {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.about-howto-steps {
  padding: var(--space-5) var(--space-6);
  border-radius: var(--radius-lg);
  background: var(--color-bg-alt);
}

.about-howto-steps-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-5);
}

.about-howto-step {
  display: flex;
  gap: var(--space-4);
  align-items: flex-start;
  margin-bottom: var(--space-5);
}

.about-howto-step:last-child {
  margin-bottom: 0;
}

.about-howto-step-num {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--color-primary);
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  margin-top: 1px;
}

.about-howto-step-text {
  font-size: 0.9rem;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.about-howto-step-detail {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}
.about-howto-step-note {
  margin-top: var(--space-2);
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* Inline key/button hint — looks like a soft keyboard key */
.about-howto-key {
  display: inline-block;
  padding: 1px var(--space-2);
  border-radius: 4px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-text);
  white-space: nowrap;
}

/* Browser compatibility note */
.about-howto-compat {
  margin-top: var(--space-6);
  padding: var(--space-4) var(--space-5);
  background: var(--color-bg-alt);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  font-size: 0.85rem;
  line-height: 1.7;
  color: var(--color-text-secondary);
}
.about-howto-compat-title {
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-2);
  font-size: 0.9rem;
}
.about-howto-compat-row {
  margin-bottom: var(--space-1);
}
.about-howto-compat-yes {
  display: inline-block;
  color: #2d8a4e;
  font-weight: 600;
  margin-right: var(--space-2);
}
.about-howto-compat-no {
  display: inline-block;
  color: #b04a4a;
  font-weight: 600;
  margin-right: var(--space-2);
}
.about-howto-compat-tip {
  margin-top: var(--space-3);
  padding-top: var(--space-3);
  border-top: 1px solid var(--color-border);
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

/* ===================================================
   SHARE SECTION — Full-width subtle background band
   to visually separate from the content grid above.
   The emotional climax of the page: free + share.
   =================================================== */
.about-share {
  background: var(--color-bg-alt);
  padding: var(--space-16) var(--space-6);
  text-align: center;
}

.about-share-inner {
  max-width: 500px;
  margin: 0 auto;
}

.about-share .about-heading {
  text-align: center;
}

.about-share-text {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  line-height: 1.8;
  margin-bottom: var(--space-4);
}

.about-share-text:last-of-type {
  margin-bottom: var(--space-5);
}

.about-free-badge {
  display: inline-block;
  padding: var(--space-2) var(--space-5);
  border-radius: 999px;
  background: rgba(130, 180, 150, 0.14);
  color: #38785e;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.03em;
}

/* ===================================================
   CREATOR — Simple, personal. No giant avatar emoji.
   Left accent line echoes the hero mission element for
   visual consistency.
   =================================================== */
.about-creator-section {
  max-width: 620px;
  margin: 0 auto;
  padding: var(--space-16) var(--space-6) var(--space-10);
}

.about-creator {
  display: flex;
  gap: var(--space-5);
  align-items: flex-start;
  padding: var(--space-5) var(--space-6);
  border-radius: var(--radius-lg);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
}

.about-creator-avatar {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  object-fit: cover;
  flex-shrink: 0;
}

.about-creator-name {
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.about-creator-bio {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.75;
  margin-bottom: var(--space-4);
}

.about-creator-links {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.about-creator-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  font-size: 0.85rem;
  color: var(--color-primary);
  text-decoration: none;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-sm);
  background: rgba(122, 107, 191, 0.08);
  min-height: var(--touch-target-sm);
}

@media (hover: hover) {
  .about-creator-link:hover {
    background: rgba(122, 107, 191, 0.15);
  }
}

/* ===================================================
   COURSE NOTE — Intentionally understated. A quiet
   footnote, not a section that competes for attention.
   Smaller heading, muted text, gentle background.
   =================================================== */
.about-note-section {
  max-width: 620px;
  margin: 0 auto;
  padding: 0 var(--space-6) var(--space-10);
}

.about-note {
  padding: var(--space-5) var(--space-6);
  border-radius: var(--radius-md);
  background: var(--color-bg-alt);
  line-height: 1.75;
}

.about-note p {
  font-size: 0.88rem;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
}

.about-note p:last-child {
  margin-bottom: 0;
}

.about-note a {
  color: var(--color-primary);
  text-decoration: none;
  font-weight: 500;
}

@media (hover: hover) {
  .about-note a:hover {
    text-decoration: underline;
  }
}

/* ===================================================
   FOOTER — Back link
   =================================================== */
.about-footer {
  max-width: 620px;
  margin: 0 auto;
  padding: 0 var(--space-6) var(--space-16);
}

.about-back {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.9rem;
  color: var(--color-primary);
  text-decoration: none;
  min-height: var(--touch-target);
}

@media (hover: hover) {
  .about-back:hover {
    text-decoration: underline;
  }
}

/* ===================================================
   FEEDBACK SECTION — Card style matching course note
   for visual consistency. Compact layout.
   =================================================== */
.about-feedback-section {
  max-width: 620px;
  margin: 0 auto;
  padding: 0 var(--space-6) var(--space-10);
}

.about-feedback-card {
  padding: var(--space-5) var(--space-6);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
}

.about-feedback-text {
  font-size: 0.88rem;
  color: var(--color-text-secondary);
  line-height: 1.75;
  margin-bottom: var(--space-4);
}

.about-feedback-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2) 0;
  min-height: var(--touch-target-sm);
  border: none;
  background: transparent;
  color: var(--color-primary);
  font-size: 0.88rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}

@media (hover: hover) {
  .about-feedback-btn:hover {
    color: var(--color-primary-dark);
  }
}

/* ===================================================
   FEEDBACK DIALOG — Modal overlay + card
   =================================================== */
.feedback-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.35);
  z-index: 9998;
  opacity: 0;
  transition: opacity 0.2s ease;
}

.feedback-overlay.show {
  display: block;
  opacity: 1;
}

.feedback-dialog {
  display: none;
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.95);
  z-index: 9999;
  width: min(440px, calc(100vw - 32px));
  max-height: calc(100vh - 48px);
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior: contain;
  scrollbar-width: none;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.14), 0 4px 12px rgba(0, 0, 0, 0.08);
  opacity: 0;
  transition: opacity 0.2s ease, transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.feedback-dialog::-webkit-scrollbar { display: none; }

.feedback-dialog.show {
  display: block;
  opacity: 1;
  transform: translate(-50%, -50%) scale(1);
}

.feedback-dialog-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--space-6) 0;
}

.feedback-dialog-title {
  font-family: var(--font-serif);
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--color-text);
}

.feedback-dialog-close {
  width: var(--touch-target-sm);
  height: var(--touch-target-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  border: none;
  background: none;
  font-size: 1.1rem;
  color: var(--color-text-muted);
  cursor: pointer;
  border-radius: var(--radius-sm);
}

@media (hover: hover) {
  .feedback-dialog-close:hover {
    background: var(--color-bg-alt);
  }
}

.feedback-dialog-body {
  padding: var(--space-5) var(--space-6) var(--space-6);
}

/* --- Login prompt --- */
.feedback-login-prompt {
  text-align: center;
  padding: var(--space-6) 0;
}

.feedback-login-prompt p {
  font-size: 0.93rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: var(--space-5);
}

.feedback-login-btn {
  padding: var(--space-3) var(--space-6);
  min-height: var(--touch-target);
  border: none;
  border-radius: var(--radius-md);
  background: var(--color-primary);
  color: #fff;
  font-size: 0.93rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}

@media (hover: hover) {
  .feedback-login-btn:hover {
    background: var(--color-primary-dark);
  }
}

/* --- Form --- */
.feedback-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.feedback-label {
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--color-text);
  margin-bottom: calc(-1 * var(--space-2));
}

.feedback-select {
  padding: var(--space-3) var(--space-4);
  min-height: var(--touch-target);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  color: var(--color-text);
  font-size: 0.93rem;
}

.feedback-select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(122, 107, 191, 0.15);
}

.feedback-textarea {
  padding: var(--space-3) var(--space-4);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  color: var(--color-text);
  font-size: 0.93rem;
  line-height: 1.65;
  resize: vertical;
  min-height: 100px;
}

.feedback-textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(122, 107, 191, 0.15);
}

.feedback-textarea::placeholder {
  color: var(--color-text-muted);
}

.feedback-form-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.feedback-time-hint {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  line-height: 1.4;
}

.feedback-submit-btn {
  padding: var(--space-3) var(--space-6);
  min-height: var(--touch-target);
  border: none;
  border-radius: var(--radius-md);
  background: var(--color-primary);
  color: #fff;
  font-size: 0.93rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  flex-shrink: 0;
}

.feedback-submit-btn:disabled {
  background: var(--color-border);
  color: var(--color-text-muted);
  cursor: default;
}

@media (hover: hover) {
  .feedback-submit-btn:not(:disabled):hover {
    background: var(--color-primary-dark);
  }
}

/* --- Success state --- */
.feedback-success {
  text-align: center;
  padding: var(--space-8) 0 var(--space-4);
}

.feedback-success-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: rgba(130, 180, 150, 0.15);
  color: #38785e;
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: var(--space-4);
}

.feedback-success-text {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
}

/* ===== Responsive: Tablet ===== */
@media (max-width: 768px) {
  .about-hero {
    padding: 96px var(--space-5) var(--space-12);
  }
  .about-hero-title {
    font-size: 1.75rem;
  }
  .about-contents {
    padding: var(--space-12) var(--space-5);
  }
  .about-share {
    padding: var(--space-12) var(--space-5);
  }
  .about-creator-section {
    padding: var(--space-12) var(--space-5) var(--space-8);
  }
  .about-howto {
    padding: var(--space-12) var(--space-5) var(--space-8);
  }
  .about-note-section {
    padding: 0 var(--space-5) var(--space-8);
  }
  .about-feedback-section {
    padding: 0 var(--space-5) var(--space-8);
  }
  .about-footer {
    padding: 0 var(--space-5) var(--space-12);
  }
}

/* ===== Responsive: Mobile ===== */
@media (max-width: 480px) {
  .about-hero {
    padding: 84px var(--space-4) var(--space-10);
  }
  .about-hero-eyebrow {
    font-size: 0.78rem;
  }
  .about-hero-title {
    font-size: 1.5rem;
  }
  .about-hero-body {
    font-size: 0.93rem;
  }
  .about-hero-mission {
    font-size: 0.9rem;
  }
  .about-heading {
    font-size: 1.2rem;
  }
  .about-contents {
    padding: var(--space-10) var(--space-4);
  }
  /* Stack grid items on phone */
  .about-grid {
    grid-template-columns: 1fr;
    gap: var(--space-2);
  }
  .about-grid-item {
    padding: var(--space-4) var(--space-3);
  }
  .about-share {
    padding: var(--space-10) var(--space-4);
  }
  .about-creator-section {
    padding: var(--space-10) var(--space-4) var(--space-6);
  }
  .about-creator {
    padding: var(--space-4);
    gap: var(--space-4);
  }
  .about-creator-avatar {
    width: 64px;
    height: 64px;
  }
  .about-howto {
    padding: var(--space-10) var(--space-4) var(--space-6);
  }
  .about-howto-grid {
    grid-template-columns: 1fr;
    gap: var(--space-3);
  }
  .about-howto-steps {
    padding: var(--space-4);
  }
  .about-note-section {
    padding: 0 var(--space-4) var(--space-6);
  }
  .about-note {
    padding: var(--space-4);
  }
  .about-feedback-section {
    padding: 0 var(--space-4) var(--space-6);
  }
  .about-feedback-card {
    padding: var(--space-4);
  }
  .about-footer {
    padding: 0 var(--space-4) var(--space-10);
  }
  .feedback-dialog-body {
    padding: var(--space-4);
  }
  .feedback-dialog-header {
    padding: var(--space-4) var(--space-4) 0;
  }
}