/* Presentation only: simulation and score replay remain v13. */
#start-screen {
  background: radial-gradient(ellipse at 50% 35%, #17394b99, transparent 60%),
    linear-gradient(0deg, #101b29 4%, #101b29f5 70%, #101b29d9);
}
#start-screen .title-wordmark {
  margin: 20px -12px 8px;
  padding: 0;
  font-size: 0;
  line-height: 0;
  transform: none;
}
.title-wordmark img { display: block; width: 100%; height: auto; }
#start-screen .eyebrow { color: #94dce6; font-size: 9px; letter-spacing: 2.1px; }
#start {
  min-height: 58px;
  margin-top: 8px;
  border: 1px solid #ffc697;
  border-radius: 14px;
  color: #271923;
  background: linear-gradient(112deg, #ffca70, #ff8a67 48%, #ff6680);
  box-shadow: 0 5px 0 #85354e, 0 9px 28px #ff855c30;
  font: 900 25px 'Barlow Condensed', sans-serif;
  letter-spacing: 3px;
  transform-origin: center;
  isolation: isolate;
}
#start:not(:disabled) { animation: start-heartbeat 1.8s ease-in-out infinite; }
#start:not(:disabled)::before {
  content: '';
  position: absolute;
  inset: -5px;
  border: 1px solid #ffc18b90;
  border-radius: 18px;
  pointer-events: none;
  animation: start-halo 1.8s ease-out infinite;
}
#start:disabled { opacity: .65; font-size: 18px; letter-spacing: 1px; }
#start:active { animation: none; transform: scale(.98); }
#start:focus-visible { outline: 3px solid #9ffaff; outline-offset: 7px; }
@keyframes start-heartbeat {
  0%, 38%, 100% { transform: scale(1); }
  10%, 24% { transform: scale(1.035); }
  17%, 31% { transform: scale(1.006); }
}
@keyframes start-halo {
  0% { transform: scale(1); opacity: .6; }
  55%, 100% { transform: scale(1.055, 1.35); opacity: 0; }
}
.start-loading {
  position: absolute;
  inset: 0;
  z-index: 20;
  display: grid;
  place-items: center;
  padding: 28px;
  text-align: center;
  background: radial-gradient(ellipse at center, #163c50, #0b1727 70%);
  outline: none;
}
.loading-content { width: min(100%, 280px); }
.loading-kicker { color: #8dc9d3; font-size: 9px; letter-spacing: 2px; }
.loading-reactor { width: 190px; height: 190px; position: relative; margin: 30px auto 22px; display: grid; place-items: center; }
.loading-reactor img { width: 100px; height: auto; filter: drop-shadow(0 0 18px #73d6ed55); animation: loading-hover 1.1s ease-in-out infinite alternate; }
.loading-ring { position: absolute; inset: 0; border: 2px solid #81edf122; border-top: 3px solid #83f4f1; border-right-color: #83f4f1; border-radius: 50%; box-shadow: 0 0 22px #73edf11a, inset 0 0 22px #73edf115; animation: loading-spin 1.35s linear infinite; }
.loading-ring.reverse { inset: 13px; border-color: #ffb17122; border-bottom: 3px solid #ffb171; animation-direction: reverse; animation-duration: 2s; }
.loading-reactor span { position: absolute; bottom: 10px; right: 15px; border: 1px solid #ffd293; background: #ffa372; color: #322033; padding: 4px 8px; font: 900 19px 'Barlow Condensed', sans-serif; transform: rotate(-12deg); border-radius: 4px; }
.loading-title { display: block; font: 900 35px 'Barlow Condensed', sans-serif; letter-spacing: 5px; color: #fff0d8; }
.loading-track { height: 4px; border-radius: 4px; background: #80e6f120; overflow: hidden; margin: 19px auto; width: 190px; }
.loading-track i { display: block; width: 45%; height: 100%; border-radius: 4px; background: linear-gradient(90deg, #80e6f1, #ffbe82); animation: loading-sweep 1.1s ease-in-out infinite; }
.loading-content p { color: #c0dce4; font-size: 12px; margin: 12px 0; }
.loading-content small { color: #789ba9; font-size: 10px; letter-spacing: 1px; }
.game[data-mode='loading'] .topbar { visibility: hidden; }
@keyframes loading-spin { to { transform: rotate(360deg); } }
@keyframes loading-hover { to { transform: translateY(-6px); } }
@keyframes loading-sweep { from { transform: translateX(-110%); } to { transform: translateX(330%); } }
@media (max-width: 360px), (max-height: 650px) {
  #start-screen .title-wordmark { margin: 12px -8px 3px; }
  #start-screen .eyebrow { font-size: 8px; letter-spacing: 1.3px; }
  #start { min-height: 52px; font-size: 23px; }
}
@media (prefers-reduced-motion: reduce) {
  #start:not(:disabled), #start:not(:disabled)::before,
  .loading-ring, .loading-reactor img, .loading-track i { animation: none; }
  #start:not(:disabled)::before { opacity: .4; }
  .loading-track i { width: 100%; opacity: .65; }
}