* {
  box-sizing: border-box;
}
html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100dvh;
  overflow: hidden;
  font-family: 'Roboto', sans-serif;
  background: #0f172a;
  -webkit-font-smoothing: antialiased;
}
.interactive {
  height: 100dvh;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 40px;
  background: #0f172a;
  overflow: hidden;
  margin: 0;
  padding: 16px;
  box-sizing: border-box;
}
.interactive aside {
  width: 280px;
  color: #f8fafc;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  height: 100%;
  max-height: 840px;
}
.brand-name {
  font-size: 38px;
  font-weight: 900;
  letter-spacing: -1.5px;
  color: #a855f7;
  margin: 0 0 2px;
}
.interactive aside > p {
  font-size: 13px;
  line-height: 1.5;
  color: #94a3b8;
  margin: 0;
  font-weight: 700;
  letter-spacing: 0.5px;
}
.interactive aside h1 {
  font-size: 26px;
  margin: 24px 0 10px;
  line-height: 1.25;
  color: #ffffff;
  font-weight: 900;
  text-wrap: balance;
}
.interactive nav {
  display: grid;
  gap: 8px;
  margin: 16px 0;
  overflow-y: auto;
  max-height: 380px;
  padding-right: 4px;
}
.interactive nav button {
  padding: 10px 14px;
  text-align: left;
  border: 1px solid #334155;
  border-radius: 12px;
  background: #1e293b;
  color: #cbd5e1;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  transition: all .2s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.interactive nav button:hover {
  background: #334155;
  color: #ffffff;
}
.interactive nav button.active {
  background: linear-gradient(135deg, #7c3aed, #6366f1);
  border-color: #a855f7;
  color: #ffffff;
  box-shadow: 0 4px 12px rgba(124, 58, 237, 0.35);
}
.interactive aside a {
  font-size: 13px;
  color: #a855f7;
  text-decoration: none;
  font-weight: 700;
  transition: color .2s ease;
}
.interactive aside a:hover {
  color: #c084fc;
}

/* Mobile / Phone Frame Container */
.player {
  width: 100%;
  max-width: 440px;
  height: 100%;
  max-height: 880px;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  position: relative;
}

#viewport {
  position: relative;
  width: 100%;
  flex: 1 1 auto;
  overflow: hidden;
  border-radius: 28px;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.4), 0 0 0 1px rgba(255, 255, 255, 0.1);
  background: #ffffff;
  display: flex;
  flex-direction: column;
}

#viewport #lesson {
  width: 100%;
  height: 100%;
  position: relative;
  overflow-y: auto;
  overflow-x: hidden;
  -webkit-overflow-scrolling: touch;
  background: #ffffff;
}

.interactive-toolbar {
  display: flex;
  gap: 8px;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  margin-top: 10px;
  padding: 0 4px;
  box-sizing: border-box;
  flex-shrink: 0;
}

#status {
  font-size: 12.5px;
  line-height: 1.4;
  text-align: center;
  color: #94a3b8;
  min-height: 18px;
  width: 100%;
  margin: 6px 0 0;
  padding: 0 8px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  flex-shrink: 0;
}

/* Responsive for Mobile Phones */
@media (max-width: 850px) {
  html, body {
    background: #ffffff;
  }
  .interactive {
    padding: 0;
    gap: 0;
    background: #ffffff;
    flex-direction: column;
    height: 100dvh;
    width: 100vw;
  }
  .interactive aside {
    display: none !important;
  }
  .player {
    max-width: 100%;
    max-height: 100dvh;
    height: 100dvh;
    padding: 0;
  }
  #viewport {
    border-radius: 0;
    box-shadow: none;
    border: none;
  }
  .interactive-toolbar {
    padding: 6px 12px;
    background: #f8fafc;
    border-top: 1px solid #e2e8f0;
    margin-top: 0;
  }
  #status {
    display: none;
  }
}