* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Fredoka", Arial, sans-serif;
  background: linear-gradient(180deg, #ffe9a3 0%, #fef6d9 100%);
  color: #2d2a44;
  min-height: 100vh;
}

:root {
  --question-font-size: 3.5rem;
  --answer-font-size: 1.75rem;
}

.app {
  max-width: 960px;
  margin: 0 auto;
  padding: 1.5rem;
  display: grid;
  gap: 1.5rem;
  position: relative;
}

.app__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.app__title {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  flex: 1 1 240px;
}

.app__title h1 {
  font-size: 2.5rem;
  margin: 0;
  color: #ff6f61;
}

.app__subtitle {
  margin: 0;
  font-weight: 500;
  max-width: 24rem;
  color: #4f4a6d;
}

.settings-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 0.25rem;
  width: 3rem;
  height: 3rem;
  border: 2px solid #7f8bff;
  border-radius: 14px;
  background: #ffffff;
  box-shadow: 0 8px 16px rgba(127, 139, 255, 0.2);
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.settings-toggle:hover,
.settings-toggle:focus-visible {
  transform: translateY(-2px);
  box-shadow: 0 12px 24px rgba(127, 139, 255, 0.28);
  border-color: #5f6fff;
  outline: none;
}

.settings-toggle__bar {
  width: 20px;
  height: 3px;
  border-radius: 999px;
  background: #5f6fff;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

.settings-toggle[aria-expanded="true"] .settings-toggle__bar:nth-of-type(1) {
  transform: translateY(6px) rotate(45deg);
}

.settings-toggle[aria-expanded="true"] .settings-toggle__bar:nth-of-type(2) {
  opacity: 0;
}

.settings-toggle[aria-expanded="true"] .settings-toggle__bar:nth-of-type(3) {
  transform: translateY(-6px) rotate(-45deg);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.controls {
  background: #ffffff;
  border-radius: 16px;
  padding: 1.25rem;
  box-shadow: 0 12px 24px rgba(255, 111, 97, 0.12);
  display: grid;
  gap: 1.25rem;
}

.controls h2 {
  margin-top: 0;
  margin-bottom: 0.75rem;
}

.controls__options {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 0.75rem;
}

.controls__option {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem;
  border: 2px solid transparent;
  border-radius: 12px;
  background: #f9f5ff;
  cursor: pointer;
  transition: border-color 0.2s ease, transform 0.2s ease;
}

.controls__option--selected {
  border-color: #7f8bff;
  box-shadow: 0 6px 12px rgba(127, 139, 255, 0.25);
}

.controls__option input {
  width: 1.25rem;
  height: 1.25rem;
}

.controls__option-details {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
}

.controls__option-title {
  font-weight: 600;
}

.controls__option-hint {
  font-size: 0.85rem;
  color: #51477f;
}

.controls__option:hover,
.controls__option:focus-within {
  border-color: #ff6f61;
  transform: translateY(-2px);
}

.controls__extras {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
  justify-content: space-between;
}

.controls__speed select {
  margin-left: 0.5rem;
  padding: 0.25rem 0.5rem;
  border-radius: 8px;
  border: 1px solid #d1c4f6;
  background: #fff;
}

.controls__start {
  background: #7f8bff;
  color: #fff;
  border: none;
  padding: 0.6rem 1.4rem;
  border-radius: 999px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 8px 16px rgba(127, 139, 255, 0.35);
  transition: transform 0.2s ease, box-shadow 0.2s ease, opacity 0.2s ease;
}

.controls__start:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 10px 20px rgba(127, 139, 255, 0.45);
}

.controls__start:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  box-shadow: none;
}

.controls__reset {
  background: #fff;
  border: 2px solid #ffbf69;
  color: #ff8c42;
  padding: 0.5rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.2s ease, transform 0.2s ease;
}

.controls__reset:hover {
  background: #ffbf69;
  color: #fff;
  transform: translateY(-1px);
}

.flashcard {
  background: #ffffff;
  border-radius: 16px;
  box-shadow: 0 12px 24px rgba(45, 42, 68, 0.1);
  padding: 1.5rem;
  display: grid;
  gap: 1.25rem;
  justify-items: center;
}

.flashcard__workspace {
  width: 100%;
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  align-items: stretch;
  flex-wrap: wrap;
}

.flashcard__card {
  position: relative;
  border-radius: 18px;
  background: radial-gradient(circle at top, #d1c4f6 0%, #9fa6f8 70%, #7f8bff 100%);
  color: #fff;
  text-align: center;
  padding: 2.25rem 1.25rem;
  overflow: hidden;
  transition: transform 0.2s ease, box-shadow 0.3s ease;
  aspect-ratio: 5 / 3;
  width: clamp(240px, 44vw, 360px);
  display: flex;
  align-items: center;
  justify-content: center;
}

.flashcard__timer {
  position: absolute;
  top: 0;
  left: 0;
  height: 8px;
  width: 100%;
  background: rgba(255, 255, 255, 0.6);
  transform-origin: left;
  transition: width 0.1s linear, opacity 0.2s ease;
}

.flashcard__timer.inactive {
  opacity: 0.3;
}

.flashcard__problem {
  font-size: clamp(2.2rem, calc(var(--question-font-size) * 0.95), 4rem);
  font-weight: 600;
  line-height: 1.1;
  margin: 0;
}

.flashcard__form {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  justify-content: center;
  gap: 0.75rem;
  border-radius: 18px;
  border: 2px solid #d1c4f6;
  background: repeating-linear-gradient(
      180deg,
      #fefbff 0,
      #fefbff 36px,
      rgba(209, 196, 246, 0.35) 37px
    ),
    #ffffff;
  box-shadow: 0 18px 32px rgba(127, 139, 255, 0.16);
  padding: 1.5rem;
  aspect-ratio: 5 / 3;
  width: clamp(240px, 44vw, 360px);
}

.flashcard__label {
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.02em;
  color: #4f4a6d;
  text-align: left;
}

#answerInput {
  padding: 0.9rem 1rem;
  font-size: var(--answer-font-size);
  border-radius: 12px;
  border: 2px solid #ccd3ff;
  text-align: center;
  width: 100%;
  min-height: 3rem;
  background: #ffffff;
  box-shadow: inset 0 0 0 1px rgba(127, 139, 255, 0.08);
}

.flashcard__actions {
  display: flex;
  gap: 0.75rem;
  margin-top: auto;
}

.flashcard__primary,
.flashcard__secondary {
  flex: 1;
  padding: 0.75rem;
  border-radius: 12px;
  border: none;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.flashcard__primary {
  background: #ff6f61;
  color: #fff;
  box-shadow: 0 8px 16px rgba(255, 111, 97, 0.3);
}

.flashcard__secondary {
  background: #ffd166;
  color: #2d2a44;
  box-shadow: 0 8px 16px rgba(255, 209, 102, 0.3);
}

.flashcard__primary:hover,
.flashcard__secondary:hover {
  transform: translateY(-2px);
}

.flashcard__feedback {
  min-height: 1.25rem;
  font-size: 1.2rem;
  font-weight: 600;
  text-align: center;
}

.flashcard__feedback--correct {
  color: #2ec4b6;
}

.flashcard__feedback--incorrect {
  color: #ef476f;
}

.scoreboard {
  background: #ffffff;
  border-radius: 16px;
  padding: 1.5rem;
  box-shadow: 0 12px 24px rgba(45, 42, 68, 0.1);
}

.scoreboard h2 {
  margin-top: 0;
}

.scoreboard ul {
  list-style: none;
  padding: 0;
  margin: 0 0 1rem;
  display: grid;
  gap: 0.5rem;
}

.scoreboard strong {
  font-size: 1.1rem;
}

.tips ul {
  margin: 0.5rem 0 0;
  padding-left: 1.2rem;
  list-style: disc;
}

.app__footer {
  text-align: center;
}

.app__footer p {
  margin-top: 0.5rem;
  color: #4f4a6d;
}

.flashcard__card--correct {
  box-shadow: 0 18px 36px rgba(46, 196, 182, 0.35);
  background: radial-gradient(circle at top, #78f5c4 0%, #44d7b6 70%, #1fb89b 100%);
  transform: scale(1.01);
}

.flashcard__card--incorrect {
  box-shadow: 0 18px 36px rgba(239, 71, 111, 0.35);
  background: radial-gradient(circle at top, #ffb3c8 0%, #ff6f91 70%, #f94b79 100%);
}

.config {
  position: absolute;
  top: 5.75rem;
  right: 1.5rem;
  width: min(360px, calc(100% - 3rem));
  background: #ffffff;
  border-radius: 18px;
  padding: 1.25rem;
  box-shadow: 0 24px 48px rgba(45, 42, 68, 0.18);
  display: grid;
  gap: 0.85rem;
  z-index: 30;
}

.config--open {
  animation: configIn 0.22s ease;
}

@keyframes configIn {
  from {
    opacity: 0;
    transform: translateY(-6px) scale(0.97);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.config[hidden] {
  display: none;
}

.config h2 {
  margin: 0;
  font-size: 1.1rem;
}

.config__grid {
  display: grid;
  gap: 0.9rem;
  grid-template-columns: 1fr;
}

.config__group {
  display: grid;
  gap: 0.6rem;
  border: none;
  margin: 0;
  padding: 0;
}

.config__group legend {
  font-weight: 600;
  color: #4f4a6d;
  font-size: 0.95rem;
}

.config__field {
  display: grid;
  gap: 0.25rem;
}

.config__field label {
  font-weight: 600;
  color: #4f4a6d;
}

.config__field select,
.config__field input[type="number"] {
  padding: 0.45rem 0.65rem;
  border: 1px solid #d1c4f6;
  border-radius: 10px;
  font-size: 0.95rem;
  font-family: inherit;
  background: #f9f5ff;
  color: #2d2a44;
}

.config__hint {
  font-size: 0.8rem;
  color: #6c648a;
  margin: 0;
}

.settings-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(45, 42, 68, 0.25);
  backdrop-filter: blur(2px);
  z-index: 20;
}

.settings-backdrop[hidden] {
  display: none;
}

@media (max-width: 768px) {
  .app {
    padding: 1rem;
  }

  .flashcard__workspace {
    flex-direction: column;
    align-items: center;
    gap: 1.25rem;
  }

  .app__header {
    align-items: flex-start;
  }

  .settings-toggle {
    width: 2.75rem;
    height: 2.75rem;
  }

  .flashcard__problem {
    font-size: calc(var(--question-font-size) * 0.75);
  }

  .flashcard__form,
  .flashcard__card {
    width: min(100%, 340px);
  }

  .flashcard__actions {
    flex-direction: column;
  }

  .config {
    right: 1rem;
    left: 1rem;
    width: auto;
  }
}