:root {
  --vurgu: #1b72f9;
  --kenar: #d5dbe3;
  --hata: #c0392b;
  --zemin: #f6f8fa;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font: 15px/1.5 system-ui, -apple-system, "Segoe UI", sans-serif;
  color: #16202c;
  background: var(--zemin);
}
header {
  background: var(--vurgu);
  color: #fff;
  padding: 14px 24px;
}
header h1 { margin: 0; font-size: 18px; font-weight: 600; }

main {
  display: grid;
  grid-template-columns: minmax(340px, 460px) 1fr;
  gap: 24px;
  padding: 24px;
  align-items: start;
}
@media (max-width: 900px) { main { grid-template-columns: 1fr; } }

form {
  background: #fff;
  border: 1px solid var(--kenar);
  border-radius: 8px;
  padding: 20px;
  display: grid;
  gap: 16px;
}
label { display: grid; gap: 6px; font-weight: 500; }
small { font-weight: 400; color: #5c6b7a; }
input, textarea {
  font: inherit;
  padding: 8px 10px;
  border: 1px solid var(--kenar);
  border-radius: 6px;
  background: #fff;
}
input:focus, textarea:focus { outline: 2px solid var(--vurgu); outline-offset: -1px; }
/* Zorunlu bir alan bos kaldiginda veya tarayicinin kendi kisitlarini (orn. amount
   input'unun min="0") ihlal ettiginde alanin kendisi kirmizilasir - #uyarilar listesi
   yalnizca sessizce dususecek satirlari (kalem/bill-to) adlandirir, alan durumunu
   tekrar etmez. */
input:invalid, textarea:invalid { border-color: var(--hata); }
input:focus:invalid, textarea:focus:invalid { outline-color: var(--hata); }
.satir { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }

fieldset { border: 1px solid var(--kenar); border-radius: 6px; padding: 12px; }
legend { font-weight: 600; padding: 0 6px; }
.kalem {
  display: grid;
  grid-template-columns: 1fr 110px 32px;
  gap: 8px;
  margin-bottom: 8px;
}
.sil {
  border: 1px solid var(--kenar);
  background: #fff;
  border-radius: 6px;
  cursor: pointer;
  font-size: 18px;
  line-height: 1;
}
.sil:hover { border-color: var(--hata); color: var(--hata); }

button { font: inherit; }
#kalem-ekle {
  justify-self: start;
  background: none;
  border: 1px dashed var(--kenar);
  border-radius: 6px;
  padding: 6px 12px;
  cursor: pointer;
  color: var(--vurgu);
}
.toplam { margin: 0; text-align: right; font-size: 17px; }
#olustur {
  background: var(--vurgu);
  color: #fff;
  border: 0;
  border-radius: 6px;
  padding: 12px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
}
#olustur:disabled { background: #9db8e0; cursor: not-allowed; }

.onizleme { position: sticky; top: 24px; }
#onizleme {
  width: 100%;
  aspect-ratio: 595.2 / 841.92;
  border: 1px solid var(--kenar);
  border-radius: 8px;
  background: #fff;
}
.hata {
  background: #fdecea;
  border-bottom: 1px solid var(--hata);
  color: var(--hata);
  padding: 12px 24px;
}
.uyari {
  margin: 0;
  padding: 10px 12px 10px 28px;
  background: #fff8e6;
  border: 1px solid #e8c98a;
  border-radius: 6px;
  color: #7a4b00;
  font-size: 14px;
}