/* === Modern CSS Reset & Base Styling === */
:root {
  /* Colors */
  --color-primary: #3171F3;
  --color-primary-dark: #bababa;
  --color-secondary: #6c757d;
  --color-success: #28a745;
  --color-danger: #dc3545;
  --color-warning: #ffc107;
  --color-info: #17a2b8;
  --color-light: #f8f9fa;
  --color-dark: #343a40;
  --color-text: #212529;
  --color-text-muted: #6c757d;
  --color-background: #ffffff;
  --color-border: #dee2e6;

  /* Typography */
  --font-family-sans-serif: "Noto Sans JP", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
  --font-size-base: 16px;
  --font-size-lg: 1.25rem;
  --font-size-sm: 0.875rem;
  --font-weight-normal: 400;
  --font-weight-bold: 700;
  --line-height-base: 1.5;

  /* Spacing */
  --spacing-1: 0.25rem;
  --spacing-2: 0.5rem;
  --spacing-3: 1rem;
  --spacing-4: 1.5rem;
  --spacing-5: 3rem;

  /* Borders */
  --border-radius: 0.375rem;
  --border-radius-sm: 0.25rem;
  --border-radius-lg: 0.5rem;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

html {
  font-size: var(--font-size-base);
}

body {
  font-family: var(--font-family-sans-serif);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-base);
  color: var(--color-text);
  background-color: var(--color-background);
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: opacity 0.2s ease;
}

a:hover {
  opacity: 0.6;
}

ul,
ol {
  list-style: none;
}

/* === Buttons === */
button {
  cursor: pointer;
  user-select: none;
  transition: opacity 0.2s ease;
  background: unset;
  border: unset;
}

button:hover {
  opacity: 0.6;
}

button.btn {
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-base);
  color: var(--color-background);
  text-align: center;
  vertical-align: middle;
  background-color: var(--color-primary);
  border: 1px solid var(--color-primary);
  padding: 0.75rem 1.5rem;
  font-size: 1rem;
  border-radius: var(--border-radius);
}

footer {
  text-align: center;
  padding: var(--spacing-4);
  text-align: center;
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  border-top: var(--border-width) solid var(--color-border);
}

header {
  height: 120px;
  display: flex;
  justify-content: flex-start;
  align-items: center;
}

main {
  height: calc(100vh - 120px);
}