@import url('https://fonts.googleapis.com/css2?family=Inter:ital,opsz,wght@0,14..32,100..900;1,14..32,100..900&display=swap');

:root {
  --bg-color: hsl(0, 0%, 95%);
  /* background off-white */
  --text-color: hsl(0, 0%, 5%);
  /* text very dark gray */
  --font-heading: 'Inter', sans-serif;
  --font-body: 'Inter', sans-serif;

  --spacing-1: 4px;
  --spacing-2: 8px;
  --spacing-3: 12px;
  --spacing-4: 16px;
  --spacing-5: 20px;
  --spacing-6: 24px;
  --spacing-8: 32px;
  --spacing-10: 40px;
  --spacing-15: 60px;
  --spacing-20: 80px;

  --color-unlearned: hsl(0, 0%, 95%);
  --color-learning: hsl(120, 60%, 75%);
  --color-learned: hsl(60, 80%, 75%);
  --color-hover: hsl(240, 100%, 50%);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-body);
  background-color: var(--bg-color);
  color: var(--text-color);
  max-width: 908px;
  margin: 0 auto;
  /* center body */
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-heading);
  margin: 16px 24px 0 0;
}

header {
  padding: var(--spacing-8) var(--spacing-4) var(--spacing-4) var(--spacing-4);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
}

header h1 {
  font-size: var(--spacing-10);
  font-weight: 700;
  text-align: left;
}

#auth-container {
  display: flex;
  align-items: center;
  gap: var(--spacing-4);
}

#user-profile {
  display: flex;
  align-items: center;
  gap: var(--spacing-5);
  font-family: var(--font-body);
  font-weight: 600;
  margin: 16px 0 0 0;
}

#login-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-2);
  padding: 8px 12px;
  margin: 16px 0 0 0;
  background-color: #fff;
  border: 2px solid #dadce0;
  cursor: pointer;
  font-size: 14px;
  font-family: var(--font-body);
  line-height: 1;
  transition: background-color 0.2s;
  white-space: nowrap;
  border-color: hsl(0, 0%, 0%);
}

#login-btn svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
  display: block;
}

#login-btn:hover {
  background-color: hsl(0, 0%, 95%);
}

#logout-btn {
  padding: var(--spacing-2) var(--spacing-3);
  background-color: hsl(0, 0%, 100%);
  border: 2px solid var(--text-color);
  color: var(--text-color);
  cursor: pointer;
  font-size: 14px;
  font-family: var(--font-body);
}

#logout-btn:hover {
  background-color: var(--text-color);
  color: var(--bg-color);
}

main {
  flex: 1;
  padding: 0 var(--spacing-4) var(--spacing-8) var(--spacing-4);
}

.top-section {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  margin-bottom: var(--spacing-5);
}

.instruction-text {
  font-size: var(--spacing-4);
  text-align: left;
}

.legend {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2);
  padding-right: var(--spacing-6);
}

.legend-row {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
  font-size: var(--spacing-4);
}

.legend-box {
  width: var(--spacing-5);
  height: var(--spacing-5);
  border: 2px solid var(--text-color);
}

@media (max-width: 600px) {
  .top-section {
    flex-direction: column-reverse;
    align-items: flex-start;
    gap: var(--spacing-4);
  }
}


.character-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, var(--spacing-10));
  gap: var(--spacing-1);
  /* small padding between boxes */
  justify-content: flex-start;
  /* left-aligned grid items */
}

.char-box {
  width: var(--spacing-10);
  height: var(--spacing-10);
  border: 2px solid var(--text-color);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--spacing-6);
  /* padding between character and box implicit in size */
  background-color: var(--color-unlearned);
  /* white by default */
  color: var(--text-color);
  /* black character */
  cursor: pointer;
  position: relative;
}

.freq-rank {
  position: absolute;
  top: 1px;
  left: 1px;
  font-size: 7px;
  line-height: 1;
  color: black;
  pointer-events: none;
  display: none;
}

.show-ranks .freq-rank {
  display: block;
}

/* Frequency rank checkbox toggle */
.freq-checkbox {
  width: var(--spacing-5);
  height: var(--spacing-5);
  border: 2px solid var(--text-color);
  background-color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.freq-checkbox.checked::after {
  content: '';
  display: block;
  width: calc(var(--spacing-5) - 8px);
  height: calc(var(--spacing-5) - 8px);
  background-color: var(--text-color);
}

.char-box:hover,
.char-box.selected-range {
  border-color: var(--color-hover);
  /* no transition time */
}

.status-learning {
  background-color: var(--color-learning);
}

.status-learned {
  background-color: var(--color-learned);
}

footer {
  padding: var(--spacing-8) var(--spacing-4);
  text-align: left;
  font-size: var(--spacing-3);
  margin-top: auto;
}

/* About button */
.about-btn-container {
  display: flex;
  justify-content: flex-end;
  padding: 0 0 0 0;
}

.about-btn {
  background: transparent;
  padding: 8px 12px;
  cursor: pointer;
  font-family: var(--font-body);
  font-size: 14px;
  color: var(--text-color);
  border: 2px solid var(--text-color);
  background-color: hsl(0, 0%, 100%);
}

.about-btn:hover {
  background-color: hsl(0, 0%, 95%);
}

.about-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1000;
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  background-color: rgba(0, 0, 0, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
}

.about-modal {
  background-color: #fff;
  border-radius: 8px;
  padding: var(--spacing-8);
  max-width: 500px;
  width: 90%;
  position: relative;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.15);
}

.about-close {
  position: absolute;
  top: var(--spacing-3);
  right: var(--spacing-4);
  background: none;
  border: none;
  font-size: 24px;
  font-family: var(--font-body);
  font-weight: 200;
  cursor: pointer;
  color: var(--text-color);
  line-height: 1;
  padding: var(--spacing-1);
}

.about-close:hover {
  opacity: 0.6;
}

.about-heading {
  font-size: 24px;
  font-weight: 600;
  margin: 0 0 var(--spacing-6) 0;
}

.about-body {
  font-size: 15px;
  line-height: 1.6;
  color: hsl(0, 0%, 25%);
}