:root {
  color-scheme: light;
  font-family: Arial, Helvetica, sans-serif;
  background: #f4f7fb;
  color: #172033;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    linear-gradient(135deg, rgba(25, 118, 210, 0.12), transparent 34%),
    linear-gradient(315deg, rgba(46, 125, 50, 0.12), transparent 32%),
    #f4f7fb;
}

button,
input {
  font: inherit;
}

button {
  border: 0;
  border-radius: 8px;
  background: #1976d2;
  color: #ffffff;
  cursor: pointer;
  font-weight: 700;
  min-height: 44px;
  padding: 0 18px;
}

button:hover {
  background: #145da6;
}

input {
  width: 100%;
  border: 1px solid #c8d2e4;
  border-radius: 8px;
  min-height: 44px;
  padding: 0 12px;
  background: #ffffff;
}

.app {
  width: min(980px, calc(100% - 32px));
  margin: 0 auto;
  padding: 32px 0;
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(260px, 0.7fr);
  gap: 18px;
}

.panel {
  background: rgba(255, 255, 255, 0.94);
  border: 1px solid #dce4f0;
  border-radius: 8px;
  box-shadow: 0 16px 38px rgba(33, 48, 77, 0.08);
}

.start-panel,
.game-panel {
  padding: 24px;
}

.brand {
  display: flex;
  gap: 16px;
  align-items: center;
}

.mark {
  width: 72px;
  height: 72px;
  border-radius: 8px;
  background: #2e7d32;
  color: #ffffff;
  display: grid;
  place-items: center;
  font-size: 24px;
  font-weight: 800;
}

h1,
h2,
p {
  margin: 0;
}

h1 {
  font-size: 34px;
  line-height: 1.08;
}

p {
  margin-top: 8px;
  color: #5a667a;
}

.start-form {
  margin-top: 28px;
}

label,
.label,
.problem-label {
  display: block;
  color: #5a667a;
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
}

.input-row,
.answer-form {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 10px;
  margin-top: 8px;
}

.game-header {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 10px;
  margin-bottom: 20px;
}

.game-header div {
  border: 1px solid #dce4f0;
  border-radius: 8px;
  padding: 12px;
  min-width: 0;
}

.game-header strong {
  display: block;
  margin-top: 4px;
  font-size: 24px;
  overflow-wrap: anywhere;
}

.problem-card {
  border: 1px solid #c8d2e4;
  border-radius: 8px;
  background: #f9fbff;
  padding: 20px;
}

.problem {
  margin-top: 10px;
  font-size: 56px;
  line-height: 1;
  font-weight: 800;
}

.answer-form {
  margin-top: 14px;
}

.answer-form input {
  font-size: 24px;
  font-weight: 700;
}

.message {
  min-height: 24px;
  margin-top: 14px;
  color: #5a667a;
  font-weight: 700;
}

.score-panel {
  padding: 18px;
}

.score-title {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}

.score-title h2 {
  font-size: 22px;
}

.score-title button {
  min-height: 36px;
  padding: 0 12px;
  background: #172033;
}

.leaderboard {
  margin: 16px 0 0;
  padding-left: 22px;
}

.leaderboard li {
  margin: 10px 0;
  padding: 10px;
  border-radius: 8px;
  background: #f4f7fb;
  font-weight: 700;
}

.leaderboard span {
  color: #5a667a;
  font-weight: 400;
}

.hidden {
  display: none;
}

@media (max-width: 760px) {
  .app {
    grid-template-columns: 1fr;
    width: min(100% - 20px, 620px);
    padding: 18px 0;
  }

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

  .mark {
    width: 56px;
    height: 56px;
    font-size: 18px;
  }

  h1 {
    font-size: 28px;
  }

  .game-header,
  .input-row,
  .answer-form {
    grid-template-columns: 1fr;
  }

  .problem {
    font-size: 46px;
  }
}