@import url("https://fonts.googleapis.com/css2?family=Mali:wght@500;700&display=swap");

/* ── Reset & tokens ───────────────────────────────────────── */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
button {
  font-family: inherit;
}

:root {
  --clr-bg: #fff8f0;
  --clr-front-1: #ff6b6b;
  --clr-front-2: #ff9f43;
  --clr-front-3: #48dbfb;
  --clr-front-4: #1dd1a1;
  --clr-front-5: #a29bfe;
  --clr-front-6: #fd79a8;
  --clr-shadow-1: #cc3e3e;
  --clr-shadow-2: #cc7318;
  --clr-shadow-3: #17aecb;
  --clr-shadow-4: #0ea578;
  --clr-shadow-5: #6c63ce;
  --clr-shadow-6: #cb4478;
  --clr-back: #d8d4cc;
  --clr-shadow-back: #a8a49c;
  --clr-back-text: #2d3436;
  --clr-white: #ffffff;
  --radius: 1.2rem;
  --transition: 0.55s cubic-bezier(0.4, 1.4, 0.6, 1);
  --focus-ring: 0 0 0 4px #fdcb6e, 0 0 0 7px #e17055;
}

/* ── Base ─────────────────────────────────────────────────── */
html {
  font-size: 18px;
}

body {
  min-height: 100dvh;
  background: var(--clr-bg);
  font-family: "Mali", cursive;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding-block: 1.5rem;
  padding-inline: 1rem;
}

/* ── Board ────────────────────────────────────────────────── */
main {
  width: 100%;
  max-width: 1200px;
  display: flex;
  flex-direction: column;
  gap: 1.4rem;
}

/* ── Top bar ──────────────────────────────────────────────── */
.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

/* shared button base */
.mode-btn,
.max-btn {
  font-size: 1.1rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 0.45rem 1.4rem;
  border: 3px solid transparent;
  border-radius: 3rem;
  background: #e0e0e0;
  color: #555;
  cursor: pointer;
  transition:
    background 0.15s,
    color 0.15s,
    transform 0.1s,
    box-shadow 0.1s;
}

.max-btn {
  font-size: 1rem;
  padding: 0.4rem 0.7rem;
  min-width: 2.4rem;
  text-transform: none;
}

.mode-btn:hover,
.max-btn:hover {
  background: #d0d0d0;
  transform: translateY(-2px);
}

.mode-btn.active {
  background: #6c5ce7;
  color: #fff;
  box-shadow: 0 4px 0 #4834d4;
}

.max-btn.active {
  background: #00b894;
  color: #fff;
  box-shadow: 0 4px 0 #00896e;
}

.mode-btn:focus-visible,
.max-btn:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.mode-btn.active:focus-visible {
  box-shadow:
    var(--focus-ring),
    0 4px 0 #4834d4;
}

.max-btn.active:focus-visible {
  box-shadow:
    var(--focus-ring),
    0 4px 0 #00896e;
}

.bottom-bar {
  display: flex;
  justify-content: space-between;
}

.type-in-control {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  cursor: pointer;
}

.type-in-label {
  font-size: 1.1rem;
  font-weight: 700;
  text-transform: uppercase;
  color: #555;
  user-select: none;
}

.type-in-toggle {
  position: relative;
  width: 3.2rem;
  height: 1.8rem;
  border: none;
  border-radius: 3rem;
  background: #c8c8c8;
  cursor: pointer;
  padding: 0;
  flex-shrink: 0;
  transition:
    background 0.25s,
    box-shadow 0.1s;
  box-shadow:
    inset 0 2px 4px rgba(0, 0, 0, 0.15),
    0 4px 0 #aaa;
}

.type-in-toggle.active {
  background: #6c5ce7;
  box-shadow:
    inset 0 2px 4px rgba(0, 0, 0, 0.2),
    0 4px 0 #4834d4;
}

.type-in-toggle:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.type-in-thumb {
  position: absolute;
  top: 0.3rem;
  left: 0.3rem;
  width: 1.2rem;
  height: 1.2rem;
  border-radius: 50%;
  background: #fff;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.25);
  transition: transform 0.25s cubic-bezier(0.4, 1.4, 0.6, 1);
}

.type-in-toggle.active .type-in-thumb {
  transform: translateX(1.4rem);
}

.board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.1rem;
  width: 100%;
}

@media (max-width: 560px) {
  .board {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ── Card shell ───────────────────────────────────────────── */
.card {
  aspect-ratio: 5 / 4;
  perspective: 900px;
  cursor: pointer;
  outline: none;
}

.card:focus-visible .card-inner {
  box-shadow: var(--focus-ring);
  border-radius: var(--radius);
}

.card[data-state="flipped"] {
  pointer-events: none;
}

/* ── Card inner (3-D flipper) ─────────────────────────────── */
.card-inner {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform var(--transition);
  border-radius: var(--radius);
  will-change: transform;
  box-shadow: 0 6px 0 var(--clr-shadow, rgba(0, 0, 0, 0.2));
}

.card[data-state="flipped"] .card-inner {
  transform: rotateY(180deg);
}

/* ── Faces ────────────────────────────────────────────────── */
.card-face {
  position: absolute;
  inset: 0;
  border-radius: var(--radius);
  backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 0.8rem;
  user-select: none;
}

/* Front face — question */
.card-front {
  color: var(--clr-white);
  font-size: clamp(1.3rem, 3.5vw, 2rem);
  font-weight: 700;
  text-shadow: 1px 2px 4px rgba(0, 0, 0, 0.2);
  gap: 0.4rem;
}

/* color cycling via nth-child */
.card:nth-child(6n + 1) .card-front {
  background: var(--clr-front-1);
}
.card:nth-child(6n + 2) .card-front {
  background: var(--clr-front-2);
}
.card:nth-child(6n + 3) .card-front {
  background: var(--clr-front-3);
}
.card:nth-child(6n + 4) .card-front {
  background: var(--clr-front-4);
}
.card:nth-child(6n + 5) .card-front {
  background: var(--clr-front-5);
}
.card:nth-child(6n + 6) .card-front {
  background: var(--clr-front-6);
}

.card:nth-child(6n + 1) .card-inner {
  --clr-shadow: var(--clr-shadow-1);
}
.card:nth-child(6n + 2) .card-inner {
  --clr-shadow: var(--clr-shadow-2);
}
.card:nth-child(6n + 3) .card-inner {
  --clr-shadow: var(--clr-shadow-3);
}
.card:nth-child(6n + 4) .card-inner {
  --clr-shadow: var(--clr-shadow-4);
}
.card:nth-child(6n + 5) .card-inner {
  --clr-shadow: var(--clr-shadow-5);
}
.card:nth-child(6n + 6) .card-inner {
  --clr-shadow: var(--clr-shadow-6);
}

.card[data-state="flipped"] .card-inner {
  --clr-shadow: var(--clr-shadow-back);
}

.card-front .question {
  font-size: clamp(1rem, 2.5vw, 1.6rem);
  transform: scale(1.5);
  transition: transform 0.3s cubic-bezier(0.4, 1.2, 0.6, 1);
}

.card[data-state="answering"] .question,
.card[data-state="flipped"] .question {
  transform: scale(1);
}

/* Answer input — hidden until card is activated */
.card-answer-clip {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.3s cubic-bezier(0.4, 1.2, 0.6, 1);
}

.card[data-state="answering"] .card-answer-clip,
.card[data-state="flipped"] .card-answer-clip {
  grid-template-rows: 1fr;
}

body[data-type-in="off"] .card[data-state="flipped"] .card-answer-clip {
  grid-template-rows: 0fr;
}

.card-answer {
  display: flex;
  align-items: stretch;
  gap: 0.4rem;
  overflow: hidden;
  opacity: 0;
  pointer-events: none;
  transform: translateY(0.4rem);
}

.card[data-state="answering"] .card-answer {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
  transition:
    opacity 0.2s 0.1s,
    transform 0.3s cubic-bezier(0.4, 1.2, 0.6, 1);
}

.card[data-state="flipped"] .card-answer {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

.card-input {
  font-family: inherit;
  font-size: clamp(1.1rem, 2.5vw, 1.5rem);
  font-weight: 700;
  width: 4rem;
  padding: 0.2rem 0.4rem;
  border: 2px solid rgba(255, 255, 255, 0.6);
  border-radius: 0.6rem;
  background: rgba(255, 255, 255, 0.25);
  color: #fff;
  text-align: center;
  outline: none;
  appearance: textfield;
}

.card-input::-webkit-outer-spin-button,
.card-input::-webkit-inner-spin-button {
  display: none;
}

.card-input:focus {
  border-color: #fff;
  background: rgba(255, 255, 255, 0.35);
}

.card-submit {
  font-family: inherit;
  font-size: clamp(1rem, 2.5vw, 1.4rem);
  font-weight: 700;
  aspect-ratio: 1;
  padding: 0;
  border: none;
  border-bottom: 4px solid #00896e;
  border-radius: 0.6rem;
  background: #00b894;
  color: #fff;
  cursor: pointer;
  line-height: 1;
  transition:
    transform 0.1s,
    filter 0.1s;
}

.card-submit:hover {
  filter: brightness(1.1);
}

.card-submit:active {
  transform: translateY(2px);
  border-bottom-width: 2px;
}

.card-submit:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

/* Back face — answer */
.card-back {
  background: var(--clr-back);
  color: var(--clr-back-text);
  transform: rotateY(180deg);
  gap: 0.35rem;
  text-align: center;
}

.card-back .guess {
  font-size: clamp(1rem, 3vw, 1.5rem);
  font-weight: 700;
  line-height: 1.3;
}

.card-back .equation {
  font-size: clamp(1rem, 3vw, 1.5rem);
  font-weight: 700;
  line-height: 1.3;
}

.card-back .answer {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 700;
  color: #e17055;
}

.card[data-correct="yes"] .card-inner {
  box-shadow:
    0 6px 0 var(--clr-shadow-back),
    0 0 0 3px #00b894;
}

.card[data-correct="no"] .card-inner {
  box-shadow:
    0 6px 0 var(--clr-shadow-back),
    0 0 0 3px #e17055;
}

.card[data-guessed] .card-back .equation {
  display: none;
}

/* ── Card animations ──────────────────────────────────────── */
@keyframes cardAppear {
  from {
    opacity: 0;
    transform: scale(0.7) rotate(-4deg);
  }
  to {
    opacity: 1;
    transform: scale(1) rotate(0deg);
  }
}

@keyframes cardExit {
  from {
    opacity: 1;
    transform: scale(1) rotate(0deg);
  }
  to {
    opacity: 0;
    transform: scale(0.7) rotate(4deg);
  }
}

.card {
  animation: cardAppear 0.45s cubic-bezier(0.4, 1.5, 0.6, 1) both;
}

.card.exiting {
  animation: cardExit 0.35s cubic-bezier(0.4, 0, 0.6, 1) both;
  pointer-events: none;
}

/* stagger via inline style --i set in JS */
.card {
  animation-delay: calc(var(--i, 0) * 55ms);
}
.card.exiting {
  animation-delay: calc(var(--i, 0) * 40ms);
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-delay: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}