body { background: radial-gradient(ellipse at 85% 0%, #f3e5cf, transparent 600px); }
.game-brand-mark { background: #fff0d6; color: #9d5d1c; font-weight: 900; }
.arithmetic-card { max-width: 850px; margin: 0 auto; padding: clamp(16px, 3vw, 28px); }
.level-picker { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 9px; margin-bottom: 20px; }
.level-picker button { display: grid; gap: 4px; min-height: 60px; padding: 10px; border: 2px solid #e6e8e0; border-radius: 13px; background: #fafbf7; color: #43584e; }
.level-picker strong { font-size: 1rem; }
.level-picker small { color: #617568; font-size: .75rem; }
.level-picker button[aria-pressed="true"] { border-color: #e7a158; background: #fff2de; color: #724515; }
.level-picker button:disabled { cursor: default; }
.challenge-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 16px; }
.score { background: #fff0d9; }
.question-card { display: grid; gap: 10px; padding: clamp(16px, 4vw, 30px); border: 1px solid #e8d7ba; border-radius: 19px; background: #fffaf0; }
.question-label { color: #836e4e; font-size: .78rem; font-weight: 800; text-transform: uppercase; letter-spacing: .1em; }
.equation { padding: 12px 0 20px; color: #433623; text-align: center; font: 900 clamp(1.8rem, 6.8vw, 3.8rem)/1.2 'Nunito', system-ui, sans-serif; font-variant-numeric: tabular-nums; letter-spacing: -.04em; white-space: nowrap; }
.expression { position: relative; display: grid; align-items: center; min-height: 150px; }
.demo-help { margin: -8px 0 12px; color: #715b3b; text-align: center; line-height: 1.6; }
.answer-feedback { position: absolute; inset: 0; display: grid; align-content: center; justify-items: center; gap: 2px; color: #b45340; }
#feedback-symbol { font: 900 106px/.95 system-ui, sans-serif; }
#feedback-label { font-size: 1rem; }
.question-card[data-phase="correct"] { border-color: #79ac8d; background: #f0faf2; }
.question-card[data-phase="correct"] .answer-feedback { color: #277b58; }
.question-card:is([data-phase="correct"], [data-phase="finished"]) .equation { visibility: hidden; }
.time-row { display: flex; align-items: center; justify-content: space-between; color: #826b47; font-size: .8rem; }
#timer { min-width: 46px; text-align: right; font-weight: 850; font-variant-numeric: tabular-nums; }
.time-track { height: 7px; border-radius: 9px; overflow: hidden; background: #eee4d3; }
#time-fill { display: block; height: 100%; width: 100%; background: #c48436; transform-origin: left; }
.question-card[data-urgent] #time-fill { background: #bc503d; }
.question-card[data-phase="finished"] { border-color: #c87c68; background: #fff3ed; }
.question-card[data-phase="finished"] #time-fill { background: #c87c68; }
.answers { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin-top: 16px; }
.answers button { display: flex; justify-content: center; align-items: center; gap: 12px; min-height: 68px; border: 2px solid transparent; border-radius: 14px; font-size: 1.3rem; font-weight: 850; }
.yes { color: #fff; background: #277b58; }
.no { color: #fff; background: #b45340; }
.answers button:hover:not(:disabled) { filter: brightness(1.09); }
.answers button:active:not(:disabled) { transform: translateY(1px); }
.answers button:disabled { opacity: .46; }
.answers button kbd { margin: 0; color: inherit; opacity: .85; font: 600 .66rem system-ui, sans-serif; }
.actions { display: flex; gap: 10px; justify-content: center; }
.message { text-align: center; min-height: 2.9em; }
#save-status { text-align: center; }
#retry { display: block; margin: 10px auto 0; }
@media (max-width: 520px) {
  .level-picker { gap: 5px; }
  .level-picker button { padding: 8px 5px; }
  .level-picker strong { font-size: .9rem; }
  .answers { gap: 8px; }
  .answers button { gap: 8px; min-height: 60px; }
  .answers button kbd { display: none; }
  .equation { padding-block: 10px 18px; }
}