/* ================================
   CSS CUSTOM PROPERTIES (VARIABLES)
   ================================ */
:root {
  /* Light mode - defaults */
  --color-bg: hsl(0, 0%, 99%);
  --color-elements: hsl(0, 100%, 100%);
  --color-text: hsl(200, 15%, 8%);
  --color-input: hsl(0, 0%, 50%);
  --color-shadow: rgba(0, 0, 0, 0.1);

  /* Typography */
  --font-family: "Nunito Sans", sans-serif;
  --font-size-body: 1.4rem;
  --font-size-detail: 1.6rem;
  --font-weight-light: 300;
  --font-weight-semibold: 600;
  --font-weight-extrabold: 800;

  /* Spacing */
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;

  /* Misc */
  --border-radius: 6px;
  --transition: all 0.2s ease;
}

/* Dark mode overrides - just swapping variables */
body.dark {
  --color-bg: hsl(207, 26%, 17%);
  --color-elements: hsl(209, 23%, 22%);
  --color-text: hsl(0, 100%, 100%);
  --color-input: hsl(0, 100%, 100%);
  --color-shadow: rgba(0, 0, 0, 0.3);
}

/* ================================
   RESET & BASE
   ================================ */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* 62.5% trick: 1rem = 10px */
html {
  font-size: 62.5%;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-body); /* 1.4rem = 14px */
  font-weight: var(--font-weight-light);
  background-color: var(--color-bg);
  color: var(--color-text);
  transition: var(--transition);
  min-height: 100vh;
}

img {
  display: block;
  max-width: 100%;
}

button {
  cursor: pointer;
  font-family: var(--font-family);
  border: none;
  background: none;
}

ul {
  list-style: none;
}

/* ================================
   NAVBAR
   ================================ */
.navbar {
  background-color: var(--color-elements);
  box-shadow: 0 2px 6px var(--color-shadow);
  padding: var(--spacing-xl) var(--spacing-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
  position: sticky;
  top: 0;
  z-index: 100;
  transition: var(--transition);
  margin-bottom: var(--spacing-lg);
}

.navbar__title {
  font-size: 1.4rem; /* 14px */
  font-weight: var(--font-weight-extrabold);
  color: var(--color-text);
}

.navbar__title-link {
  color: inherit;
  text-decoration: none;
  display: inline-block;
}

.navbar__title-link:hover {
  opacity: 0.8;
}

.theme-toggle {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: 1.3rem; /* 13px */
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  transition: var(--transition);
}

.theme-toggle:hover {
  opacity: 0.7;
}

/* ================================
   MAIN LAYOUT
   ================================ */
.main {
  padding: var(--spacing-lg);
  max-width: 1440px;
  margin: 0 auto;
}

/* ================================
   CONTROLS (search + filter)
   ================================ */
.controls {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

/* Search box */
.search-box {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  background-color: var(--color-elements);
  border-radius: var(--border-radius);
  padding: var(--spacing-md) var(--spacing-lg);
  box-shadow: 0 2px 6px var(--color-shadow);
  transition: var(--transition);
}

.search-box__icon {
  font-size: 1.6rem; /* 16px */
  color: var(--color-input);
  flex-shrink: 0;
}

.search-box__input {
  border: none;
  outline: none;
  background: none;
  font-family: var(--font-family);
  font-size: var(--font-size-body);
  font-weight: var(--font-weight-light);
  color: var(--color-text);
  width: 100%;
}

.search-box__input::placeholder {
  color: var(--color-input);
}

/* Filter dropdown */
.filter__select {
  background-color: var(--color-elements);
  color: var(--color-text);
  border: none;
  outline: none;
  border-radius: var(--border-radius);
  padding: var(--spacing-md) var(--spacing-lg);
  font-family: var(--font-family);
  font-size: var(--font-size-body);
  font-weight: var(--font-weight-light);
  box-shadow: 0 2px 6px var(--color-shadow);
  cursor: pointer;
  width: fit-content;
  min-width: 12rem;
  transition: var(--transition);
  /* custom arrow */
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23888' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 1rem center;
  padding-right: 2.5rem;
}

/* ================================
   COUNTRIES GRID
   ================================ */
.countries-grid {
  display: grid;
  /* single column on mobile */
  grid-template-columns: 1fr;
  gap: var(--spacing-xl);
  /* center cards on mobile */
  max-width: 32rem;
  margin: 0 auto;
}

/* ================================
   COUNTRY CARD
   ================================ */
.card {
  background-color: var(--color-elements);
  border-radius: var(--border-radius);
  box-shadow: 0 2px 8px var(--color-shadow);
  overflow: hidden;
  cursor: pointer;
  transition:
    transform 0.2s ease,
    box-shadow 0.2s ease;
  text-decoration: none;
  color: inherit;
  display: block;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 20px var(--color-shadow);
}

.card__flag {
  width: 100%;
  height: 16rem; /* 160px */
  object-fit: cover;
}

.card__body {
  padding: var(--spacing-lg) var(--spacing-lg) var(--spacing-xl);
}

.card__name {
  font-size: 1.6rem; /* 16px */
  font-weight: var(--font-weight-extrabold);
  margin-bottom: var(--spacing-md);
}

.card__info {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.card__info p {
  font-size: var(--font-size-body);
  color: var(--color-text);
}

.card__info strong {
  font-weight: var(--font-weight-semibold);
}

/* ================================
   BACK BUTTON (detail page)
   ================================ */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  background-color: var(--color-elements);
  color: var(--color-text);
  padding: var(--spacing-sm) var(--spacing-xl);
  border-radius: var(--border-radius);
  box-shadow: 0 2px 6px var(--color-shadow);
  font-size: var(--font-size-body);
  font-weight: var(--font-weight-light);
  margin-bottom: var(--spacing-xl);
  transition: var(--transition);
}

.back-btn:hover {
  opacity: 0.7;
}

/* ================================
   COUNTRY DETAIL (detail page)
   ================================ */
.country-detail {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xl);
}

.country-detail__flag {
  width: 100%;
  border-radius: var(--border-radius);
  box-shadow: 0 4px 16px var(--color-shadow);
}

.country-detail__info {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.country-detail__name {
  font-size: 2.4rem; /* 24px */
  font-weight: var(--font-weight-extrabold);
}

.country-detail__stats {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xl);
}

.country-detail__group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
  font-size: var(--font-size-detail);
}

.country-detail__group p {
  font-weight: var(--font-weight-light);
}

.country-detail__group strong {
  font-weight: var(--font-weight-semibold);
}

/* Border countries */
.country-detail__borders {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.country-detail__borders h3 {
  font-size: var(--font-size-detail);
  font-weight: var(--font-weight-semibold);
}

.borders-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
}

.border-btn {
  background-color: var(--color-elements);
  color: var(--color-text);
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--border-radius);
  box-shadow: 0 2px 6px var(--color-shadow);
  font-size: 1.2rem; /* 12px */
  font-weight: var(--font-weight-light);
  transition: var(--transition);
}

.border-btn:hover {
  opacity: 0.7;
}

/* ================================
   LOADING & ERROR STATES
   ================================ */
.state-message {
  text-align: center;
  padding: var(--spacing-xl);
  color: var(--color-input);
  font-size: 1.6rem; /* 16px */
  grid-column: 1 / -1;
}