:root {
  --paper: #efe7d6;
  --line: rgba(31, 34, 38, 0.10);
  --card: rgba(255, 255, 255, 0.78);
  --shadow: 0 18px 60px rgba(31, 34, 38, 0.10);
  --ink: #1f2226;
  --ink-soft: #586168;
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  background: linear-gradient(180deg, #f8f4ea 0%, var(--paper) 100%);
  font-family: "Avenir Next", "Segoe UI", "Helvetica Neue", sans-serif;
  color: var(--ink);
}

.page-shell {
  width: min(100%, 1500px);
  min-height: 100%;
  margin: 0 auto;
  padding: 8px;
}

.frame-panel,
.help-panel {
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--card);
  box-shadow: var(--shadow);
}

.frame-panel {
  padding: 0;
  overflow: hidden;
}

#app-frame {
  display: block;
  width: 100%;
  height: calc(100vh - 16px);
  border: none;
  background: #fff;
}

.help-panel {
  max-width: 720px;
  margin: 32px auto;
  padding: 24px;
}

h1 {
  margin: 0 0 12px;
  font-family: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Georgia, serif;
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 0.95;
}

p {
  margin: 0 0 10px;
  color: var(--ink-soft);
  line-height: 1.55;
}

code {
  background: rgba(31, 34, 38, 0.08);
  border-radius: 8px;
  padding: 2px 6px;
}

@media (max-width: 900px) {
  .page-shell {
    padding: 0;
  }

  .frame-panel {
    border: none;
    border-radius: 0;
    box-shadow: none;
  }

  #app-frame {
    height: 100vh;
  }
}