:root{
  --bg: #f3f4f6;
  --panel: #ffffff;
  --border: #e5e7eb;
  --text: #111827;
  --muted: #6b7280;
  --link: #2563eb;
  --user: #2563eb;
  --userText: #ffffff;
  --assistant: #f9fafb;
  --shadow: 0 10px 30px rgba(0,0,0,0.08);
}

*{ box-sizing: border-box; }

html, body{
  height: 100%;
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Ubuntu, Cantarell, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}

/* Zentrierter Rahmen, skaliert gut bis 4k */
.shell{
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  width: min(1100px, calc(100vw - 32px));
  margin: 0 auto;
  padding: 18px 0;
}

/* Header immer sichtbar und lesbar */
.topbar{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 12px 14px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: var(--shadow);
}

.brand{
  font-weight: 700;
  font-size: 18px;
}

.topmeta{
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
  color: var(--muted);
  white-space: nowrap;
}

.toplink{
  color: var(--link);
  text-decoration: none;
  font-weight: 600;
}
.toplink:hover{ text-decoration: underline; }
.sep{ color: #9ca3af; }

/* Hauptkarte */
.card{
  margin-top: 14px;
  flex: 1;
  display: flex;
  flex-direction: column;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

/* Chat Bereich: nimmt Platz, scrollt sauber */
.chat{
  flex: 1;
  overflow-y: auto;
  padding: 18px;
  background: linear-gradient(#ffffff, #fbfbfd);
}

/* Bubbles: gut lesbar, nicht zu breit auf 4k */
.bubble{
  max-width: 78%;
  padding: 12px 14px;
  border-radius: 12px;
  margin: 10px 0;
  line-height: 1.45;
  font-size: 15px;
  border: 1px solid var(--border);
  white-space: pre-wrap;
  word-break: break-word;
}

.bubble.assistant{
  background: var(--assistant);
  color: var(--text);
}

.bubble.user{
  margin-left: auto;
  background: var(--user);
  border-color: rgba(37,99,235,0.35);
  color: var(--userText);
}

/* Composer unten */
.composer{
  display: flex;
  gap: 10px;
  padding: 14px;
  border-top: 1px solid var(--border);
  background: #f8fafc;
}

.composer input[type="text"]{
  flex: 1;
  padding: 12px 14px;
  font-size: 15px;
  border-radius: 10px;
  border: 1px solid var(--border);
  outline: none;
  background: #ffffff;
  color: var(--text);
}

.composer input[type="text"]::placeholder{
  color: var(--muted);
}

.composer button{
  padding: 12px 16px;
  font-size: 15px;
  font-weight: 700;
  border: none;
  border-radius: 10px;
  background: var(--user);
  color: #ffffff;
  cursor: pointer;
}

.composer button:hover{
  filter: brightness(0.95);
}

.composer button:disabled{
  opacity: 0.6;
  cursor: not-allowed;
}

/* Mobile: voller, weniger Rand, Bubbles breiter */
@media (max-width: 640px){
  .shell{
    width: calc(100vw - 20px);
    padding: 12px 0;
  }
  .topbar{
    flex-direction: column;
    align-items: flex-start;
  }
  .chat{
    padding: 14px;
  }
  .bubble{
    max-width: 92%;
  }
  .composer{
    flex-direction: column;
  }
  .composer button{
    width: 100%;
  }
}