/* ==========================================================================
   howto.css — #howto
   応募方法 — FINAL バナー → 家型コンテナの中に 7ラウンド
   ========================================================================== */

.opg-howto {
  background: var(--opg-paper);
  position: relative;
  overflow: hidden;
}

/* Soft rainbow glow on backdrop */
.opg-howto::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 10% 30%, oklch(72% 0.18 350 / 0.18), transparent 55%),
    radial-gradient(ellipse at 90% 70%, oklch(70% 0.14 210 / 0.18), transparent 55%);
  pointer-events: none;
}

.opg-flow {
  position: relative;
  max-width: 900px;
  margin: 60px auto 0;
  display: flex;
  flex-direction: column;
  align-items: center;
}

/* FINAL banner (top) */
.opg-flow__final {
  position: relative;
  z-index: 2;
  background: var(--opg-ink);
  color: #fff;
  border-radius: var(--opg-radius-pill);
  padding: 20px 48px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  box-shadow: 0 24px 60px -20px rgba(0,0,0,0.45);
  text-align: center;
  max-width: 720px;
  width: 100%;
}
.opg-flow__final-title {
  font-size: clamp(15px, 1.8vw, 19px);
  font-weight: 900;
  letter-spacing: 0.02em;
}
.opg-flow__final-date {
  font-family: var(--opg-font-en);
  font-size: var(--opg-text-sm);
  font-weight: 700;
  letter-spacing: 0.08em;
  background: var(--opg-grad-rainbow);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

/* House (pentagon: pointed top → 予選会の勝者が FINAL へ集結する暗喩) */
.opg-flow__house {
  position: relative;
  margin-top: -28px;
  padding: 80px clamp(24px, 5vw, 56px) 56px;
  background: rgba(255,255,255,0.7);
  border: 1px solid var(--opg-border);
  box-shadow: 0 30px 80px -30px rgba(0,0,0,0.25);
  backdrop-filter: blur(10px);
  width: 100%;
  /* pentagon shape with pointed top */
  clip-path: polygon(50% 0, 100% 14%, 100% 100%, 0 100%, 0 14%);
  z-index: 1;
}

.opg-flow__heading {
  text-align: center;
  margin-bottom: 36px;
}
.opg-flow__eyebrow {
  font-size: 20px;
  font-weight: 900;
  letter-spacing: 0.04em;
  margin-bottom: 8px;
}
.opg-flow__lead {
  font-size: var(--opg-text-sm);
  color: var(--opg-ink-soft);
  line-height: 1.8;
  margin: 0;
  max-width: 620px;
  margin-inline: auto;
}

/* 7 round circles — 4 + 3 layout (centered) */
.opg-flow__rounds {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: clamp(16px, 2.4vw, 28px);
  margin: 0 auto;
  padding: 0;
  list-style: none;
  max-width: 720px;
}
.opg-flow__rounds li {
  flex: 0 0 calc((100% - clamp(16px, 2.4vw, 28px) * 3) / 4);
  min-width: 0;
}
@media (max-width: 720px) {
  .opg-flow__rounds li {
    flex-basis: calc((100% - clamp(16px, 2.4vw, 28px)) / 2);
  }
}

.opg-flow__round {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  width: 100%;
}

.opg-flow__round-date {
  font-size: var(--opg-text-sm);
  font-weight: 700;
  color: var(--opg-ink-soft);
  letter-spacing: 0.02em;
  text-align: center;
  line-height: 1.3;
}

.opg-flow__rounds li {
  display: flex;
  justify-content: center;
}

.opg-flow__disc {
  position: relative;
  width: 100%;
  aspect-ratio: 1;
  border-radius: 50%;
  display: grid;
  place-items: center;
  color: #fff;
  font-weight: 900;
  font-size: clamp(14px, 1.6vw, 17px);
  letter-spacing: -0.01em;
  text-align: center;
  box-shadow: 0 20px 50px -18px rgba(0,0,0,0.4);
  overflow: hidden;
  transition: transform 0.3s ease;
}
.opg-flow__disc::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 50%;
  background: radial-gradient(circle at 30% 25%, rgba(255,255,255,0.45), transparent 55%);
}
.opg-flow__rounds li:hover .opg-flow__disc {
  transform: translateY(-4px) scale(1.04);
}

@media (max-width: 560px) {
  .opg-flow__house {
    clip-path: polygon(50% 0, 100% 9%, 100% 100%, 0 100%, 0 9%);
    padding-top: 60px;
  }
  .opg-flow__final { padding: 16px 24px; }
}