:root {
  --fsp-bg: #f7f6f2;
  --fsp-surface: #ffffff;
  --fsp-border: #d8d4cc;
  --fsp-text: #28251d;
  --fsp-muted: #7a7974;
  --fsp-primary: #01696f;
  --fsp-primary-hover: #0c4e54;
  --fsp-radius: 20px;
  --fsp-radius-sm: 14px;
  --fsp-shadow: 0 16px 38px rgba(40, 37, 29, 0.08);
}

.fsp-shell {
  max-width: 760px;
  margin: 20px auto;
  padding: 12px;
  background: transparent;
  color: var(--fsp-text);
  font: 16px/1.5 Arial, sans-serif;
}

.fsp-header {
  margin-bottom: 14px;
}

.fsp-header h2 {
  margin: 0 0 4px;
  font-size: 16px;
  line-height: 1.35;
  font-weight: 700;
}

.fsp-header p {
  margin: 0;
  font-size: 14px;
  color: var(--fsp-muted);
}

.fsp-toolbar {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 16px;
}

.fsp-toolbar select,
.fsp-toolbar button,
.fsp-card-btn {
  width: 100%;
  min-height: 46px;
  padding: 12px 14px;
  border: 1px solid var(--fsp-border);
  border-radius: var(--fsp-radius-sm);
  background: #fff;
  color: var(--fsp-text);
  font: inherit;
  box-sizing: border-box;
  appearance: none;
}

.fsp-toolbar select:focus,
.fsp-toolbar button:focus,
.fsp-card-btn:focus {
  outline: none;
  border-color: var(--fsp-primary);
  box-shadow: 0 0 0 3px rgba(1, 105, 111, 0.14);
}

#fsp-load {
  background: var(--fsp-primary);
  color: #fff;
  border-color: var(--fsp-primary);
}

.fsp-cards {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.fsp-study-card {
  perspective: 1200px;
}

.fsp-study-card-inner {
  position: relative;
  width: 100%;
  min-height: 0;
  height: auto;
  transform-style: preserve-3d;
  transition: transform 0.45s ease;
}

.fsp-study-card.is-flipped .fsp-study-card-inner {
  transform: rotateY(180deg);
}

.fsp-study-face {
  position: relative;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  background: var(--fsp-surface);
  border: 1px solid var(--fsp-border);
  border-radius: var(--fsp-radius);
  box-shadow: var(--fsp-shadow);
  padding: 22px 18px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  gap: 16px;
  min-height: 180px;
}

.fsp-study-front {
  cursor: pointer;
}

.fsp-study-front-text {
  font-size: 16px;
  line-height: 1.45;
  font-weight: 600;
  word-break: break-word;
  max-width: 28ch;
  margin: 0 auto;
}

.fsp-study-back {
  position: absolute;
  inset: 0;
  transform: rotateY(180deg);
}

.fsp-study-answer {
  font-size: 16px;
  line-height: 1.45;
  padding: 14px 16px;
  border-radius: 14px;
  background: #f3f0ec;
  min-height: 56px;
  width: 100%;
  max-width: 28ch;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  word-break: break-word;
}

.fsp-masked {
  background: #0b0b0b;
  color: #0b0b0b;
  user-select: none;
}

.fsp-blurred {
  filter: blur(2.5px);
}

.fsp-study-actions {
  display: flex;
  gap: 10px;
  width: 100%;
  justify-content: center;
  flex-wrap: wrap;
}

.fsp-card-btn {
  min-height: 42px;
  padding: 10px 12px;
  cursor: pointer;
  width: auto;
  min-width: 88px;
}

.fsp-card-btn:active,
#fsp-load:active {
  transform: translateY(1px);
}

.fsp-loading,
.fsp-empty {
  font-size: 14px;
  color: var(--fsp-muted);
  text-align: center;
  padding: 12px 0;
}

.fsp-sentinel {
  height: 1px;
}

@media (min-width: 768px) {
  .fsp-shell {
    max-width: 900px;
    padding: 20px;
  }

  .fsp-toolbar {
    flex-direction: row;
    align-items: center;
  }

  .fsp-toolbar select,
  .fsp-toolbar button {
    width: auto;
  }

  .fsp-study-face {
    min-height: 220px;
    padding: 28px 24px;
  }
}