:root {
      --gradient-bg: linear-gradient(135deg, #7f7fd5 0%, #91eae4 100%);
      --primary: #ffd600;
      --accent: #ffd600;
      --secondary: #ffd600;
      --text-color: #fff;
      --button-text-color: #343434;
    }
    body {
      background-image: var(--gradient-bg);
      background-size: cover;
      background-repeat: no-repeat;
      background-position: center;
      margin: 0;
      min-height: 100vh;
      font-family: Arial, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 0;
    }
    .welcome-banner {
      width: 100%;
      text-align: center;
      margin: 0 auto 40px auto;
      padding-top: 42px;
      padding-bottom: 14px;
    }
    .welcome-title {
      color: #ffd700;
      font-size: 2.6rem;
      font-weight: 900;
      letter-spacing: 0.018em;
      text-shadow: 0 2px 18px rgba(60,60,60, 0.13);
      margin-bottom: 13px;
    }
    .welcome-description {
      color: #e8ecf7;
      font-size: 1.25rem;
      font-weight: 500;
      margin-bottom: 24px;
    }
.link-buttons-row {
  display: flex;
  justify-content: center;
  gap: 28px;
  flex-wrap: wrap;
  margin-top: 11px;
}
.link-button {
  text-decoration: none;
  background: #ffd600;
  color: #2c2f36;
  padding: 19px 33px;
  font-size: 1.27rem;
  font-weight: 700;
  border: none;
  border-radius: 18px;
  box-shadow: 0 8px 24px rgba(80,80,150,0.15);
  cursor: pointer;
  transition: filter 0.12s, transform 0.13s;
  margin-bottom: 14px;
}
.link-button:hover {
  color:#0077ff;
  filter: brightness(0.94);
  transform: translateY(-2px) scale(1.04);
}
    @media (max-width: 1100px) {
      .welcome-title { font-size: 2.2rem; }
      .welcome-description { font-size: 1.1rem;}
      .link-buttons-row { gap: 19px;}
      .link-button { font-size: 1.15rem; padding: 17px 24px; }
    }
    @media (max-width: 650px) {
      .welcome-banner { margin-bottom: 12px; padding-top: 28px;}
      .welcome-title { font-size: 1.15rem; }
      .welcome-description { font-size: 0.91rem;}
      .link-buttons-row { gap: 10px;}
      .link-button { font-size: 1rem; padding: 11px 8vw;}
    }
.container {
      background: transparent;
      box-shadow: none;
      border-radius: 20px;
      max-width: 900px;
      width: 100%;
      text-align: center;
      padding: 0;
      margin-top: 0;
    }
    h2 {
      color: var(--primary);
      font-size: 2.1rem;
      font-weight: 700;
      margin-bottom: 26px;
      margin-top: 18px;
      text-shadow: 0 3px 18px rgba(60,60,60, 0.09);
      letter-spacing: 0.02em;
    }
    .toggle-buttons {
      display: flex;
      justify-content: center;
      gap: 32px;
      margin-bottom: 34px;
    }
    .toggle-btn {
      background: var(--accent);
      color: var(--button-text-color);
      border: none;
      border-radius: 15px;
      padding: 18px 36px;
      font-weight: 700;
      font-size: 1.18rem;
      box-shadow: 0 2px 16px rgba(80,80,80,0.11);
      cursor: pointer;
      transition: filter 0.2s, transform 0.15s;
      outline: none;
      user-select: none;
      letter-spacing: 0.01em;
      margin-bottom: 0;
    }
    .toggle-btn.active, .toggle-btn:hover {
      filter: brightness(0.92);
      transform: translateY(-2px) scale(1.03);
    }
    .solver-section {
      display: none;
      text-align: center;
      margin: 0 auto;
      max-width: 540px;
      background: rgba(255,255,255,0.04);
      border-radius: 18px;
      padding: 24px 22px 20px 22px;
      box-shadow: 0 4px 30px rgba(70,70,150,0.10);
    }
    .solver-section.active {
      display: block;
      background: transparent;
      color: #fafaff;
    }
    label {
      font-weight: 600;
      color: var(--text-color);
      display: block;
      margin-bottom: 12px;
      font-size: 1.05rem;
    }
    .inputs-row {
      display: flex;
      align-items: center;
      justify-content: center;
      flex-wrap: nowrap;
      margin: 16px 0 0 0;
      gap: 8px;
    }
    .inputs-row span {
      font-weight: 700;
      color: var(--button-text-color);
      margin-right: 0;
      user-select: none;
      font-size: 1.12rem;
      white-space: nowrap;
    }
    input[type=number], select {
      padding: 8px 10px;
      font-size: 1.06rem;
      border: 1px solid #c0c9ea;
      border-radius: 6px;
      text-align: center;
      width: 70px;
      margin-right: 0;
      background: #f6faff;
      color: #393939;
    }
    select {
      width: auto;
      text-align: left;
      padding-left: 10px;
    }
    button.solve-btn {
      margin-top: 32px;
      padding: 16px 0;
      width: 100%;
      background: linear-gradient(90deg, var(--accent), var(--secondary));
      border: none;
      border-radius: 13px;
      color: var(--button-text-color);
      font-weight: 700;
      font-size: 1.22rem;
      cursor: pointer;
      box-shadow: 0 4px 14px rgba(80,80,150,0.14);
      transition: filter 0.13s, transform 0.13s;
    }
    button.solve-btn:hover {
      filter: brightness(0.92);
      transform: translateY(-1.5px) scale(1.01);
      background: linear-gradient(90deg, #ffe766, #ffe766);
    }
    .result {
      margin-top: 20px;
      font-weight: 600;
      color: #fff;
      min-height: 40px;
      white-space: pre-line;
      font-size: 1.12rem;
      text-shadow: 0 2px 8px rgba(60,60,60, 0.10);
    }
    .equation-row {
      margin-bottom: 12px;
    }