.diffeq-formula-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  margin-bottom: 18px;
  margin-top: 23px;
  font-size: 1.16em;
  flex-wrap: wrap;
}
.diffeq-frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  font-size: 1em;
  font-weight: 500;
  margin-right: 3px;
  margin-left: 3px;
  line-height: 1;
  min-width: 28px;
}
.diffeq-frac-num {
  font-size: 0.98em;
  font-family: inherit;
  padding-bottom: 0.2em;
}
.diffeq-frac-bar {
  border-top: 2.1px solid #222;
  width: 21px;
  height: 0;
  margin: 0;
}
.diffeq-frac-den {
  font-size: 0.98em;
  font-family: inherit;
  padding-top: 0.2em;
}
.diffeq-eq {
  font-size: 1.18em;
  font-weight: 600;
  color: #4267e9;
  margin: 0 8px 0 8px;
}
.diffeq-f-input {
  width: 220px;
  font-size: 1em;
  padding: 7px 14px;
  border-radius: var(--radius);
  border: 1px solid #e3e6ee;
  margin-right: 10px;
  background: #fff;
  transition: border 0.2s;
}
.diffeq-f-input:focus {
  border: 1.5px solid #4267e9;
  outline: none;
}
.diffeq-ic {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 1em;
  color: #222;
}
.diffeq-ic input[type="number"] {
  width: 54px;
  font-size: 1em;
  margin: 0 3px;
  border-radius: 7px;
  border: 1px solid #e3e6ee;
  padding: 4px 7px;
  background: #fff;
  transition: border 0.2s;
}
.diffeq-ic input[type="number"]:focus {
  border: 1.5px solid #4267e9;
  outline: none;
}
@media (max-width: 650px) {
  .diffeq-formula-row {
    flex-direction: column;
    align-items: stretch;
    gap: 7px;
    font-size: 1em;
  }
  .diffeq-ic input[type="number"], .diffeq-f-input {
    width: 100%;
    min-width: 0;
    margin-right: 0;
    margin-left: 0;
  }
  .diffeq-ic {
    justify-content: flex-start;
  }
}
/* Остальной стиль графика и кнопок */
#diffeq-graph-container {
  position: relative;
  width: 100%;
  max-width: 540px;
  margin: 0 auto 12px auto;
  height: 340px;
  background: linear-gradient(135deg, #e3f0ff 0%, #f8fafc 100%);
  border-radius: 15px;
  box-shadow: 0 4px 28px rgba(66,103,233,0.13);
  transition: box-shadow .2s;
  display: none;
  overflow: hidden;
}
#diffeq-graph-container.active {
  display: block;
  animation: fadeIn .7s;
}
#diffeq-graph {
  display: block;
  margin: 0 auto;
  background: transparent;
  border-radius: 12px;
  border: none;
  width: 100%;
  max-width: 540px;
  height: 340px;
  cursor: crosshair;
  transition: filter .2s;
  box-shadow: none;
}
.graph-tooltip {
  position: absolute;
  background: #fff;
  color: #222;
  font-size: 1em;
  border: 1.5px solid #4267e9;
  border-radius: 8px;
  padding: 3px 13px;
  pointer-events: none;
  box-shadow: 0 2px 12px rgba(66,103,233,0.15);
  z-index: 4;
  white-space: nowrap;
  transition: opacity 0.13s;
  opacity: 0;
  font-family: inherit;
}
.center-btn-row {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 12px;
  margin-top: 13px;
  margin-bottom: 5px;
  flex-wrap: wrap;
}
/* .step-btn { */
/*   background: #e3e6ee; */
/*   color: #a0a6b8; */
/*   border: none; */
/*   padding: 10px 24px; */
/*   border-radius: var(--radius); */
/*   font-size: 1.09em; */
/*   font-weight: 600; */
/*   cursor: not-allowed; */
/*   box-shadow: 0 1px 8px rgba(66,103,233,0.07); */
/*   opacity: .68; */
/*   transition: none; */
/*   pointer-events: none; */
/*   user-select: none; */
/* } */
#diffeq-result {
  margin-top: 0;
  min-height: 0;
  transition: min-height .3s;
  padding-bottom: 0;
  display: none;
  justify-content: center;
  align-items: flex-start;
}
#diffeq-result.active {
  display: flex;
  min-height: 56px;
  padding-bottom: 14px;
  animation: fadeIn .6s;
}
@keyframes fadeIn {
  0% {opacity:0; transform:translateY(30px);}
  100% {opacity:1; transform:translateY(0);}
}
@media (max-width: 650px) {
  #diffeq-graph-container, #diffeq-graph { max-width: 98vw; }
  .center-btn-row { flex-direction: column; gap: 7px; }
}