:root {
  --steps: 4;              /* Total number of steps */
  --gap: 1rem;             /* Spacing between fields */
  --accent: #2563eb;       /* Progress + focus color */
  --track: #e5e7eb;        /* Progress track color */
  --bg: #ffffff;           /* Form background */
  --muted: #6b7280;        /* Muted text */
  --radius: 12px;          /* Corner radius */
  --shadow: 0 10px 25px rgba(0,0,0,0.08);
}

/* Container */
.form-wrap {
  width: min(720px, 100%);
  background: var(--bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  border: 1px solid #e5e7eb;
}

/* Header + progress */
.form-header {
  padding: 1rem 1.25rem;
  border-bottom: 1px solid #e5e7eb;
  background: #fafafa;
}
.title {
  font-size: 1.125rem;
  font-weight: 600;
  margin: 0 0 0.5rem;
}
.subtitle {
  color: var(--muted);
  font-size: 0.95rem;
  margin: 0 0 0.75rem;
}

.progress {
  height: 8px;
  border-radius: 999px;
  background: var(--track);
  overflow: hidden;
  position: relative;
}
.progress > span {
  position: absolute;
  inset: 0 auto 0 0;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), #22c55e);
  border-radius: inherit;
  transition: width 350ms ease;
}

/* Track area */
.viewport {
  position: relative;
  width: 100%;
  overflow: hidden;
}
.track {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 100%;
  width: 100%;
  transform: translateX(0%);
  transition: transform 400ms ease;
}

/* Step panel */
.step {
  padding: 1.25rem;
  display: grid;
  gap: var(--gap);
}
.step h2 {
  margin: 0 0 0.25rem;
  font-size: 1.05rem;
}
.step p {
  margin: 0 0 0.75rem;
  color: var(--muted);
}

/* Fields */
.field {
  display: grid;
  gap: 0.375rem;
}
.field label {
  font-size: 0.95rem;
  line-height: 1em;
  color: #374151;
}
.input,
select,
textarea {
  width: 100%;
  padding: 0.65rem 0.75rem;
  border: 1px solid #d1d5db;
  border-radius: 8px;
  background: #fff;
  font-size: 1.5rem;
  transition: border-color 150ms ease, box-shadow 150ms ease;
}
.input:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}
textarea {
  min-height: 110px;
  resize: vertical;
}

/* Nav */
.nav {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 1rem 1.25rem;
  border-top: 1px solid #e5e7eb;
  background: #fafafa;
}
.btn {
  appearance: none;
  border: none;
  border-radius: 10px;
  padding: 0.7rem 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 50ms ease, box-shadow 150ms ease, background 150ms ease;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}
.btn:active { transform: scale(0.98); }

.btn-next {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.2);
}
.btn-prev {
  background: #e5e7eb;
  color: #111827;
}
.btn-submit {
  background: #22c55e;
  color: #fff;
  box-shadow: 0 6px 16px rgba(34, 197, 94, 0.24);
}

/* Hide radio controls */
.steps { display: none; }

/* Slide + progress states driven by :checked */
#s1:checked ~ .form-wrap .track { transform: translateX(0%); }
#s2:checked ~ .form-wrap .track { transform: translateX(-100%); }
#s3:checked ~ .form-wrap .track { transform: translateX(-200%); }
#s4:checked ~ .form-wrap .track { transform: translateX(-300%); }

#s1:checked ~ .form-wrap .progress > span { width: calc(100% / var(--steps) * 1); }
#s2:checked ~ .form-wrap .progress > span { width: calc(100% / var(--steps) * 2); }
#s3:checked ~ .form-wrap .progress > span { width: calc(100% / var(--steps) * 3); }
#s4:checked ~ .form-wrap .progress > span { width: calc(100% / var(--steps) * 4); }

/* Conditional nav visibility */
#s1:checked ~ .form-wrap .nav .prev { visibility: hidden; }
#s4:checked ~ .form-wrap .nav .next { display: none; }
#s4:checked ~ .form-wrap .nav .submit { display: inline-flex; }
.submit { display: none; }

/* Hide all nav labels initially */
.nav .prev label,
.nav .next label {
  display: none;
}

/* Show correct NEXT button */
#s1:checked ~ .form-wrap .nav .next label[for="s2"] { display: inline-flex; }
#s2:checked ~ .form-wrap .nav .next label[for="s3"] { display: inline-flex; }
#s3:checked ~ .form-wrap .nav .next label[for="s4"] { display: inline-flex; }

/* Show correct PREV button */
#s2:checked ~ .form-wrap .nav .prev label[for="s1"] { display: inline-flex; }
#s3:checked ~ .form-wrap .nav .prev label[for="s2"] { display: inline-flex; }
#s4:checked ~ .form-wrap .nav .prev label[for="s3"] { display: inline-flex; }