:root {
  --bg: #f4f8f5;
  --card: #ffffff;
  --text: #1a1f1c;
  --accent: #0f766e;
  --accent-dark: #0b5e58;
  --border: #cfe1d9;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Atkinson Hyperlegible", "Segoe UI", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 10% 10%, #e6f6ee 0%, transparent 40%),
    radial-gradient(circle at 90% 0%, #dff4ef 0%, transparent 35%),
    var(--bg);
  min-height: 100vh;
}

.container {
  max-width: 760px;
  margin: 2.5rem auto;
  padding: 0 1.1rem 2rem;
}

h1 {
  margin: 0 0 1rem;
  font-size: clamp(1.8rem, 2vw + 1rem, 2.5rem);
}

.panel {
  margin-top: 1rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.1rem;
  box-shadow: 0 10px 25px rgba(16, 24, 40, 0.07);
}

.panel h2 {
  margin-top: 0;
}

.panel p {
  line-height: 1.45;
}

.actions {
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
  margin-top: 0.8rem;
}

#lesson-progress,
#lesson-target,
#lesson-feedback {
  font-weight: 600;
}

#lesson-stats {
  font-weight: 600;
  color: var(--accent-dark);
}

#key-output {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--accent);
  margin: 0.7rem 0;
}

.panel button {
  padding: 0.62rem 1rem;
  border: 1px solid var(--accent-dark);
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  font: inherit;
  cursor: pointer;
}

.btn {
  display: inline-block;
  padding: 0.62rem 1rem;
  border: 1px solid var(--accent-dark);
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  font: inherit;
  text-decoration: none;
}

.panel button:hover {
  background: var(--accent-dark);
}

.btn:hover {
  background: var(--accent-dark);
}

input {
  width: 100%;
  margin-top: 0.35rem;
  padding: 0.65rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  font: inherit;
}

select {
  width: 100%;
  margin-top: 0.35rem;
  margin-bottom: 0.6rem;
  padding: 0.65rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  font: inherit;
  background: #fff;
}

.checkline {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  margin-top: 0.3rem;
}

.checkline input[type='checkbox'] {
  width: 1.2rem;
  height: 1.2rem;
  margin: 0;
}

.panel button:focus-visible,
.btn:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 3px solid #0a7f3f;
  outline-offset: 2px;
}

.panel[hidden] {
  display: none;
}

#end-section {
  border-color: #b9decf;
  background: #f2fbf6;
}

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