/* =========================
LAYOUT ZONES (CORE SYSTEM)
========================= */

.action-box {
  width: 100%;

  display: flex;
  flex-direction: column;
  align-items: center;

  padding: 0 0 40px;

  background:
    linear-gradient(
      180deg,
      rgba(18, 35, 55, 0.92),
      rgba(10, 22, 36, 0.96)
    );

  border: 1px solid rgba(255,255,255,0.06);

  border-radius: 32px;

  box-shadow:
    0 30px 80px rgba(0,0,0,0.35),
    inset 0 1px 0 rgba(255,255,255,0.04);

  backdrop-filter: blur(18px);

  overflow: visible;
  isolation: isolate;
}

/* =========================
SECTION HEADER
========================= */

.section-header-zone {
  display: flex;
  justify-content: center;

  padding-top: 24px;
}

/* =========================
TOP CONTENT
========================= */

.top-zone {
  text-align: center;

  display: flex;
  flex-direction: column;
  align-items: center;

  gap: 8px;

  padding-top: 8px;
}

.top-layout-zone {
  width: 100%;

  display: flex;
  align-items: center;
  justify-content: center;

  gap: 40px;

  padding:
    10px 40px 0;
}

.side-left-zone,
.side-right-zone {
  width: 110px;
  height: 110px;

  flex-shrink: 0;

  border-radius: 24px;

  background:
    linear-gradient(
      180deg,
      rgba(255,255,255,0.04),
      rgba(255,255,255,0.02)
    );

  border:
    1px solid rgba(255,255,255,0.05);

  backdrop-filter:
    blur(12px);

  box-shadow:
    inset 0 1px 0 rgba(255,255,255,0.04),
    0 10px 30px rgba(0,0,0,0.18);
}

.side-control-zone {
  display: grid;
  grid-template-columns: 1fr 1fr;
  align-items: center;
  justify-items: center;

  gap: 10px;

  padding: 10px;

  background:
    linear-gradient(
      180deg,
      rgba(6,14,24,0.42),
      rgba(8,20,34,0.28)
    );

  border:
    1px solid rgba(255,255,255,0.07);

  box-shadow:
    inset 0 1px 0 rgba(255,255,255,0.05),
    inset 0 -1px 0 rgba(0,0,0,0.32),
    0 14px 34px rgba(0,0,0,0.22);
}

/* =========================
HERO
========================= */

.lesson-hero-right {
  display: flex;
  justify-content: center;
}

.lesson-hero-grid {
  display: grid;

  grid-template-columns:
    minmax(0, 1.1fr)
    minmax(360px, 500px);

  gap: 80px;

  align-items: center;
}

.lesson-hero-left,
.lesson-hero-right {
  min-width: 0;
}

/* =========================
KEYBOARD CONTROLS
========================= */

.keyboard-controls-zone {
  width: auto;

  display: flex;
  align-items: center;
  justify-content: center;

  padding: 10px 18px;

  background:
    rgba(255,255,255,0.04);

  border:
    1px solid rgba(255,255,255,0.06);

  border-radius:
    999px;

  backdrop-filter:
    blur(12px);

  box-shadow:
    0 12px 30px rgba(0,0,0,0.25);
}

.center-zone {
  display: flex;
  width: 100%;
  flex-direction: column;
  align-items: center;

  gap: 0;

  margin-top: 28px;
}

/* =========================
MICRO HELP — ACTION SIDE
========================= */

.micro-help-zone {
  position: relative;

  display: flex;
  align-items: center;
  justify-content: center;
}

.micro-help-btn {
  width: 46px;
  height: 46px;

  display: flex;
  align-items: center;
  justify-content: center;

  border: 1px solid rgba(255,255,255,0.12);
  border-radius: 999px;

  background:
    rgba(255,255,255,0.06);

  color:
    rgba(255,225,68,0.92);

  font-family: inherit;
  font-size: 24px;
  line-height: 1;

  cursor: pointer;

  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);

  box-shadow:
    0 10px 28px rgba(0,0,0,0.22),
    inset 0 1px 0 rgba(255,255,255,0.06);

  transition:
    transform 0.22s ease,
    background 0.22s ease,
    color 0.22s ease,
    box-shadow 0.22s ease;
}

.micro-help-btn:hover {
  transform: translateY(-2px) scale(1.04);

  background:
    rgba(255,225,68,0.92);

  color:
    #111;

  box-shadow:
    0 16px 36px rgba(255,225,68,0.20);
}

.micro-help-box {
  position: absolute;
  left: 50%;
  bottom: calc(100% + 14px);

  width: min(300px, calc(100vw - 48px));
  max-height: 140px;
  overflow-y: auto;

  padding: 14px 16px;

  border-radius: 18px;

  background: rgba(10,22,36,0.94);

  border: 1px solid rgba(255,255,255,0.10);

  color: rgba(255,255,255,0.82);

  font-size: 13px;
  line-height: 1.55;
  font-weight: 600;

  text-align: left;

  box-shadow: 0 20px 50px rgba(0,0,0,0.36);

  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);

  opacity: 0;
  transform: translateX(-50%) translateY(-4px) scale(0.98);

  pointer-events: none;

  transition:
    opacity 0.22s ease,
    transform 0.22s ease;

  z-index: 80;
}

.micro-help-box.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0) scale(1);
  pointer-events: auto;
}

@media (max-width: 768px) {
  .micro-help-box {
    width: min(280px, calc(100vw - 32px));
    max-height: 130px;
    font-size: 12.5px;
    line-height: 1.5;
  }

  #actionMotif .bottom-zone {
    gap: 14px;
  }
}

/* =========================
BOTTOM + FEEDBACK
========================= */

.bottom-zone {
  margin-top: 34px;
  margin-bottom: 10px;

  display: flex;
  flex-direction: column;
  align-items: center;

  gap: 6px;
}
#actionMotif .bottom-zone {
  gap: 22px;
}
.feedback-zone {
  display: flex;
  justify-content: center;

  margin-top: 0;
}

/* =========================
CONTENT WIDTH SYSTEM
========================= */

.content-section .container--narrow {
  max-width: 1040px;
}

.content-section p {
  max-width: 720px;
}

.content-section .section-heading h2 {
  max-width: 760px;
}

/* =========================
UNDERSTANDING LAYOUT
========================= */

.understanding-box {
  display: grid;

  grid-template-columns:
  minmax(0, 1fr)
  minmax(220px, 320px);

  gap: 80px;

  align-items: center;

}

.understanding-content {
  min-width: 0;
}

.understanding-visuals {
  display: flex;
  flex-direction: column;

  gap: 20px;
}

.understanding-visual-card {
  overflow: hidden;

  border-radius: 28px;

  background:
    rgba(255,255,255,0.42);

  border:
    1px solid rgba(15,23,42,0.06);

  box-shadow:
    0 20px 50px rgba(15,23,42,0.08);
}

.understanding-visual-card img {
  width: 100%;

  aspect-ratio: 4 / 3;

  object-fit: cover;

  display: block;
}

/* =========================
UNDERSTANDING VIDEO
========================= */

.understanding-video-card {
  max-width: 320px;
  margin-left: auto;
  margin-right: auto;
}

.understanding-video {
  width: 100%;
  height: auto;
  max-height: 260px;

  display: block;

  object-fit: cover;

  border-radius: inherit;
}

@media (max-width: 768px) {
  .understanding-video-card {
    max-width: 280px;
  }

  .understanding-video {
    max-height: 220px;
  }
}

/* =========================
UNDERSTANDING — MEDIA ROW VARIANT
tekst u góry, trzy video pod spodem
========================= */

.understanding-box--media-row {
  grid-template-columns: 1fr;
  gap: 34px;
}

.understanding-box--media-row .understanding-content {
  max-width: 860px;
}

.understanding-box--media-row .understanding-content p {
  max-width: 820px;
}

.understanding-media-row {
  width: 100%;

  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));

  gap: 18px;
}

.understanding-media-card {
  padding: 18px;

  border-radius: 24px;

  background:
    rgba(255,255,255,0.42);

  border:
    1px solid rgba(15,23,42,0.06);

  box-shadow:
    0 18px 42px rgba(15,23,42,0.08);
}

.understanding-media-label {
  margin-bottom: 6px;

  font-size: 12px;

  font-weight: 800;

  letter-spacing: 0.08em;

  text-transform: uppercase;

  color:
    rgba(15,23,42,0.44);
}

.understanding-media-title {
  margin-bottom: 12px;

  font-size: clamp(18px, 2vw, 24px);

  font-weight: 800;

  letter-spacing: -0.04em;

  color:
    rgba(15,23,42,0.88);
}

.understanding-media-video {
  width: 100%;

  display: block;

  border-radius: 18px;

  background:
    rgba(15,23,42,0.08);
}

@media (max-width: 900px) {
  .understanding-media-row {
    grid-template-columns: 1fr;
  }

  .understanding-media-card {
    padding: 16px;
  }
}

/* =========================
UNDERSTANDING — STACKED VARIANT
tekst u góry, obraz na całą szerokość
========================= */

.understanding-box--stacked {
  grid-template-columns: 1fr;
  gap: 18px;
}

.understanding-box--stacked .understanding-content {
  max-width: 860px;
}

.understanding-box--stacked .understanding-content p {
  max-width: 820px;
}

.understanding-box--stacked .understanding-visuals {
  width: 100%;
}

.understanding-box--stacked .understanding-visual-card {
  width: 100%;
}

.understanding-box--stacked .understanding-visual-card img {
  width: 100%;
  height: auto;
  aspect-ratio: auto;
  object-fit: contain;
}

/* Lesson 1 — Understanding image size */
#understandKeys .understanding-box--stacked .understanding-visual-card img {
  width: 72%;
  max-width: 760px;
  height: auto;
  margin: 0 auto;
  object-fit: contain;
}

#understandCF .understanding-image-cf {
  width: min(100%, 760px);
  max-height: 320px;
  margin: 0 auto;
  object-fit: contain;
}

@media (min-width: 901px) and (max-height: 820px) {
  #understandCF .understanding-image-cf {
    max-height: 240px;
  }
}

/* =========================
   UNDERSTANDING STACKED — COMPACT DESKTOP HEIGHT
   keeps stacked understand sections inside one viewport on shorter laptops
========================= */

@media (min-width: 901px) and (max-height: 820px) {
  .understanding-box--stacked {
    gap: 12px;
  }

  .understanding-box--stacked .understanding-content {
    max-width: 900px;
  }

  .understanding-box--stacked .understanding-content .section-label {
    margin-bottom: 18px;
  }

  .understanding-box--stacked .understanding-content h3 {
    margin-bottom: 16px;
    font-size: clamp(30px, 3vw, 42px);
  }

  .understanding-box--stacked .understanding-content p {
    font-size: 15px;
    line-height: 1.65;
    max-width: 900px;
  }

  .understanding-box--stacked .understanding-content p + p {
    margin-top: 10px;
  }

  .understanding-box--stacked .understanding-visuals {
    gap: 12px;
  }

  .understanding-box--stacked .understanding-video-card {
    max-width: 280px;
  }

  .understanding-box--stacked .understanding-video {
    max-height: 190px;
  }

  .understanding-box--stacked .audio-explain {
    margin-top: 14px;
  }

  .understanding-box--stacked .audio-explain-btn {
    height: 42px;
    padding: 0 18px;
    font-size: 13px;
  }
}

/* =========================
REFERENCE NOTES
========================= */

.ebook-content {
  padding:
    clamp(34px, 4vw, 52px);
  max-width: 760px;

  margin-left: auto;
}

.ebook-content h2 {
  margin:
    22px 0 34px;

  font-size:
    clamp(34px, 4vw, 48px);

  line-height:
    1;

  letter-spacing:
    -0.04em;
}

.ebook-list {
  display: flex;
  flex-direction: column;

  gap: 20px;
}

.ebook-section {
  padding-bottom: 26px;

  border-bottom:
    1px solid rgba(15,23,42,0.08);
}

.ebook-section:last-child {
  border-bottom: none;

  padding-bottom: 0;
}

.ebook-item-top {
  display: flex;
  align-items: center;

  gap: 16px;

  margin-bottom: 10px;
}

.ebook-number {
  font-size: 13px;

  font-weight: 800;

  letter-spacing: 0.08em;

  color:
    rgba(15,23,42,0.34);
}

.ebook-section h3 {
  margin: 0;

  font-size: 20px;

  letter-spacing: -0.03em;
}

.ebook-section p {
  margin: 0;

  padding-left: 34px;

  font-size: 14px;

  line-height: 1.8;

  color:
    rgba(15,23,42,0.68);

  max-width:
    620px;
}

/* =========================
MINI THEORY — TWO COLUMN VARIANT
========================= */

#miniTheory .mini-theory-layout {
  display: grid;
  grid-template-columns: minmax(260px, 0.9fr) minmax(0, 1.1fr);
  gap: 32px;
  align-items: stretch;
}

#miniTheory .mini-theory-card {
  padding: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
}

#miniTheory .mini-theory-card img {
  width: 100%;
  max-width: 360px;
  height: auto;
  object-fit: contain;
}

#miniTheory .ebook-content {
  max-width: none;
  margin-left: 0;
}

#miniTheory .ebook-content .section-label {
  margin-bottom: 32px;
}

/* =========================
   MINI THEORY — COMPACT DESKTOP HEIGHT
   keeps memory card section inside one viewport on shorter laptops
========================= */

@media (min-width: 901px) and (max-height: 820px) {
  #miniTheory {
    padding: 48px 0;
  }

  #miniTheory .mini-theory-layout {
    gap: 24px;
    align-items: center;
  }

  #miniTheory .mini-theory-card {
    padding: 22px;
  }

  #miniTheory .mini-theory-card img {
    max-width: 320px;
    max-height: 520px;
    object-fit: contain;
  }

  #miniTheory .card-actions {
    margin-top: 14px;
    gap: 10px;
  }

  #miniTheory .card-actions .action-btn {
    min-height: 40px;
    padding: 8px 12px;
    font-size: 13px;
  }

  #miniTheory .ebook-content {
    padding: 34px 38px;
  }

  #miniTheory .ebook-content .section-label {
    margin-bottom: 24px;
  }

  #miniTheory .ebook-list {
    gap: 14px;
  }

  #miniTheory .ebook-section {
    padding-bottom: 18px;
  }

  #miniTheory .ebook-item-top {
    margin-bottom: 8px;
  }

  #miniTheory .ebook-section h3 {
    font-size: 19px;
  }

  #miniTheory .ebook-section p {
    font-size: 13.5px;
    line-height: 1.65;
  }
}

/* =========================
video card
========================= */

.video-card {
  transform:
    scale(1.04);
}

/* =========================
CONTROL TIP — ONE-TIME MICRO TUTORIAL
========================= */

/* =========================
CONTROL TIP — PLAY / STOP
========================= */

.has-control-tip {
  position: relative;
}

.control-tip {
  position: absolute;

  left: 50%;
  bottom: calc(100% + 12px);

  transform: translateX(-50%);

  width: max-content;
  max-width: 160px;

  padding: 8px 12px;

  border-radius: 999px;

  background: rgba(255,225,68,0.96);
  color: rgba(15,23,42,0.94);

  font-size: 12px;
  line-height: 1.25;
  font-weight: 800;

  text-align: center;

  box-shadow:
    0 12px 28px rgba(255,225,68,0.28),
    0 0 0 1px rgba(255,255,255,0.22);

  z-index: 70;

  pointer-events: none;

  animation:
    controlTipNudge 1.4s ease-in-out 0s 4,
    controlTipNudge 1.4s ease-in-out infinite;
}

.control-tip::after {
  content: "";

  position: absolute;

  left: 50%;
  top: calc(100% - 1px);

  transform: translateX(-50%);

  width: 0;
  height: 0;

  border-left: 8px solid transparent;
  border-right: 8px solid transparent;
  border-top: 9px solid rgba(255,225,68,0.96);
}

.control-tip::before {
  display: none;
}

@keyframes controlTipNudge {
  0% {
    transform: translateX(-50%) translateY(0);
  }

  50% {
    transform: translateX(-50%) translateY(-5px);
  }

  100% {
    transform: translateX(-50%) translateY(0);
  }
}

@keyframes controlTipFade {
  to {
    opacity: 0;
    visibility: hidden;
  }
}

@media (max-width: 768px) {
  .action-box {
    padding: 0 0 28px;
    border-radius: 26px;
    overflow: visible;
  }

  .section-header-zone {
    padding-top: 18px;
  }

  .top-zone {
    width: 100%;
    padding-top: 6px;
    gap: 6px;
  }

  .top-layout-zone {
    width: 100%;
    display: grid;
    grid-template-columns: auto minmax(0, 1fr) auto;
    align-items: center;
    justify-content: stretch;
    gap: 14px;
    padding: 8px 18px 0;
  }

  .side-left-zone,
  .side-right-zone {
    width: 78px;
    height: 78px;
    border-radius: 22px;
  }

  .side-control-zone {
    gap: 8px;
    padding: 8px;
  }

  .keyboard-controls-zone {
    gap: 8px;
    padding: 8px 12px;
  }

  .center-zone {
    width: 100%;
    margin-top: 18px;
  }

  .bottom-zone {
    margin-top: 24px;
    margin-bottom: 6px;
    gap: 8px;
  }

  .micro-help-btn {
    width: 42px;
    height: 42px;
    font-size: 22px;
  }
}

@media (max-width: 420px) {
  .top-layout-zone {
    gap: 10px;
    padding-left: 14px;
    padding-right: 14px;
  }

  .side-left-zone,
  .side-right-zone {
    width: 68px;
    height: 68px;
    border-radius: 20px;
  }
}

@media (max-width: 768px) {
  .top-layout-zone {
    grid-template-columns: minmax(0, 72px) minmax(0, 1fr) minmax(0, 72px);
    gap: 10px;
    padding-left: 14px;
    padding-right: 14px;
    overflow: hidden;
  }

  .side-left-zone,
  .side-right-zone {
    width: 72px;
    height: 72px;
    min-width: 0;
    flex-shrink: 1;
  }

  .side-control-zone {
    width: 72px;
    height: 72px;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
    padding: 7px;
  }

  .side-control-zone .action-btn.btn-play,
  .side-control-zone .action-btn.btn-stop {
    width: 30px;
    height: 30px;
    border-radius: 10px;
    font-size: 13px;
  }

  .center-zone {
    margin-top: 12px;
  }

  .bottom-zone {
    margin-top: 18px;
  }

  #actionMotif .bottom-zone {
    gap: 14px;
  }
}

@media (max-width: 420px) {
  .top-layout-zone {
    grid-template-columns: minmax(0, 64px) minmax(0, 1fr) minmax(0, 64px);
    gap: 8px;
    padding-left: 12px;
    padding-right: 12px;
  }

  .side-left-zone,
  .side-right-zone,
  .side-control-zone {
    width: 64px;
    height: 64px;
  }

  .side-control-zone .action-btn.btn-play,
  .side-control-zone .action-btn.btn-stop {
    width: 28px;
    height: 28px;
    font-size: 12px;
  }

  .center-zone {
    margin-top: 10px;
  }

  .bottom-zone {
    margin-top: 14px;
  }
}

@media (max-width: 768px) {
  .top-layout-zone {
    grid-template-columns: 86px minmax(0, 1fr) 64px;
    gap: 8px;
    padding-left: 12px;
    padding-right: 12px;
    overflow: visible;
  }

  .side-left-zone {
    width: 86px;
    height: 56px;
    min-width: 0;
    border-radius: 18px;
  }

  .side-right-zone {
    width: 64px;
    height: 64px;
    min-width: 0;
    border-radius: 20px;
  }

  .side-control-zone {
    width: 86px;
    height: 56px;
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
    gap: 6px;
    padding: 6px;
  }

  .side-control-zone .action-btn.btn-play,
  .side-control-zone .action-btn.btn-stop {
    flex: 0 0 auto;
    width: 34px;
    height: 34px;
    border-radius: 11px;
    font-size: 13px;
  }

  .micro-help-zone {
    position: relative;
  }

  .micro-help-box {
    left: auto;
    right: 0;
    bottom: calc(100% + 12px);
    transform: translateY(-4px) scale(0.98);
    width: min(300px, calc(100vw - 32px));
    max-width: calc(100vw - 32px);
    max-height: 150px;
    overflow-y: auto;
  }

  .micro-help-box.show {
    transform: translateY(0) scale(1);
  }
}

@media (max-width: 420px) {
  .top-layout-zone {
    grid-template-columns: 80px minmax(0, 1fr) 58px;
    gap: 7px;
    padding-left: 10px;
    padding-right: 10px;
  }

  .side-left-zone,
  .side-control-zone {
    width: 80px;
    height: 54px;
  }

  .side-right-zone {
    width: 58px;
    height: 58px;
  }

  .side-control-zone .action-btn.btn-play,
  .side-control-zone .action-btn.btn-stop {
    width: 32px;
    height: 32px;
    font-size: 12px;
  }

  .micro-help-box {
    right: -4px;
    width: min(280px, calc(100vw - 24px));
    max-width: calc(100vw - 24px);
  }
}

@media (max-width: 768px) {
  #miniTheory .mini-theory-layout {
    display: grid;
    grid-template-columns: 1fr;
    gap: 26px;
    align-items: stretch;
  }

  #miniTheory .mini-theory-card {
    width: 100%;
    max-width: 100%;
    padding: 22px;
    align-items: center;
    justify-content: center;
    overflow: hidden;
  }

  #miniTheory .mini-theory-card img {
    width: 100%;
    max-width: min(100%, 360px);
    height: auto;
    max-height: 520px;
    object-fit: contain;
    margin: 0 auto;
  }

  #miniTheory .ebook-content {
    width: 100%;
    max-width: 100%;
    margin-left: 0;
    padding: 30px 24px;
  }

  #miniTheory .ebook-content .section-label {
    margin-bottom: 22px;
  }

  #miniTheory .ebook-content h2 {
    font-size: clamp(30px, 9vw, 42px);
    line-height: 0.98;
    margin: 18px 0 26px;
  }

  #miniTheory .ebook-list {
    gap: 16px;
  }

  #miniTheory .ebook-section {
    padding-bottom: 20px;
  }

  #miniTheory .ebook-item-top {
    gap: 12px;
    margin-bottom: 8px;
  }

  #miniTheory .ebook-section h3 {
    font-size: 18px;
    line-height: 1.15;
  }

  #miniTheory .ebook-section p {
    padding-left: 0;
    font-size: 14.5px;
    line-height: 1.65;
  }

  #miniTheory .card-actions {
    grid-template-columns: 1fr;
    gap: 10px;
    margin-top: 16px;
  }

  #miniTheory .card-actions .action-btn {
    width: 100%;
    min-height: 42px;
    padding: 10px 14px;
    font-size: 14px;
  }
}

@media (max-width: 420px) {
  #miniTheory .mini-theory-layout {
    gap: 22px;
  }

  #miniTheory .mini-theory-card {
    padding: 18px;
  }

  #miniTheory .mini-theory-card img {
    max-width: 100%;
    max-height: 460px;
  }

  #miniTheory .ebook-content {
    padding: 26px 20px;
  }

  #miniTheory .ebook-content h2 {
    font-size: clamp(28px, 8.5vw, 38px);
  }

  #miniTheory .ebook-section p {
    font-size: 14px;
    line-height: 1.6;
  }
}

@media (max-width: 768px) {
  .understanding-box {
    display: grid;
    grid-template-columns: 1fr;
    gap: 24px;
    padding: 34px 26px;
  }

  .understanding-content {
    width: 100%;
    max-width: 100%;
  }

  .understanding-box h3 {
    font-size: clamp(32px, 9.5vw, 44px);
    line-height: 0.98;
    letter-spacing: -0.045em;
    margin-bottom: 18px;
  }

  .understanding-box p {
    max-width: 100%;
    font-size: 15.5px;
    line-height: 1.65;
  }

  .understanding-box p + p {
    margin-top: 12px;
  }

  .understanding-visuals {
    width: 100%;
    gap: 16px;
  }

  .understanding-visual-card {
    width: 100%;
    border-radius: 24px;
  }

  .understanding-box--stacked .understanding-visual-card img,
  .understanding-visual-card img {
    width: 100%;
    max-height: 260px;
    object-fit: contain;
  }

  #understandKeys .understanding-box--stacked .understanding-visual-card img {
    width: 100%;
    max-width: 100%;
    max-height: 260px;
  }

  .understanding-video-card {
    width: 100%;
    max-width: 100%;
    margin-left: auto;
    margin-right: auto;
  }

  .understanding-video,
  .understanding-media-video {
    width: 100%;
    max-height: 240px;
    object-fit: contain;
  }

  .video-frame iframe {
    height: 220px;
  }

  .audio-explain {
    margin-top: 18px;
  }

  .audio-explain-btn {
    width: min(100%, 360px);
    min-height: 42px;
    height: auto;
    padding: 11px 18px;
    font-size: 13.5px;
    line-height: 1.2;
    white-space: normal;
    text-align: center;
  }
}

@media (max-width: 420px) {
  .understanding-box {
    gap: 20px;
    padding: 30px 22px;
  }

  .understanding-box h3 {
    font-size: clamp(30px, 9vw, 40px);
    margin-bottom: 16px;
  }

  .understanding-box p {
    font-size: 15px;
    line-height: 1.6;
  }

  .understanding-box--stacked .understanding-visual-card img,
  .understanding-visual-card img,
  #understandKeys .understanding-box--stacked .understanding-visual-card img {
    max-height: 230px;
  }

  .understanding-video,
  .understanding-media-video {
    max-height: 220px;
  }

  .video-frame iframe {
    height: 200px;
  }

  .audio-explain {
    margin-top: 16px;
  }

  .audio-explain-btn {
    width: 100%;
    font-size: 13px;
  }
}

@media (min-width: 769px) and (max-width: 1024px) {
  .action-box {
    padding-bottom: 34px;
    border-radius: 30px;
  }

  .section-header-zone {
    padding-top: 20px;
  }

  .top-layout-zone {
    gap: 26px;
    padding: 10px 28px 0;
  }

  .side-left-zone,
  .side-right-zone {
    width: 92px;
    height: 92px;
    border-radius: 22px;
  }

  .side-control-zone {
    gap: 8px;
    padding: 9px;
  }

  .center-zone {
    margin-top: 22px;
  }

  .bottom-zone {
    margin-top: 26px;
  }

  .micro-help-box {
    max-width: 320px;
  }

  .understanding-box {
    gap: 42px;
    padding: 42px;
  }

  #miniTheory .mini-theory-layout {
    gap: 26px;
  }

  #miniTheory .mini-theory-card {
    padding: 24px;
  }

  #miniTheory .ebook-content {
    padding: 34px;
  }
}