/* Reset and Base Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-main);
  color: var(--text-main);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-lg);
  line-height: 1.5;
}

@media (min-width: 1024px) {
  body {
    padding: var(--spacing-2xl);
  }
}

.container {
  max-width: 1152px; /* 6xl */
  width: 100%;
  margin: 0 auto;
}

/* Header */
header {
  margin-bottom: var(--spacing-2xl);
}

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

.header-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.logo {
  width: 2rem;
  height: 2rem;
  object-fit: contain;
}

@media (min-width: 768px) {
  .logo {
    width: 2.5rem;
    height: 2.5rem;
  }
}

header h1 {
  font-size: 1.875rem; /* 3xl */
  font-weight: 800;
  letter-spacing: -0.025em;
  color: var(--primary-colour);
}

.theme-toggle {
  background: none;
  border: 2px solid var(--border-colour);
  border-radius: var(--border-radius-md);
  padding: var(--spacing-sm);
  cursor: pointer;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-speed);
}

.theme-toggle:hover {
  background-color: var(--bg-subtle);
  color: var(--primary-colour);
}

.theme-toggle .moon-icon {
  display: none;
}

[data-theme="dark"] .theme-toggle .sun-icon {
  display: none;
}

[data-theme="dark"] .theme-toggle .moon-icon {
  display: block;
}

.header-accent {
  height: 0.25rem;
  width: 5rem;
  background-color: var(--accent-colour);
  margin-top: var(--spacing-md);
}

/* Layout */
.main-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-2xl);
  align-items: start;
}

@media (min-width: 1024px) {
  .main-layout {
    grid-template-columns: repeat(12, 1fr);
    gap: 4rem;
  }
}

.calculator-inputs {
  display: flex;
  flex-direction: column;
}

@media (min-width: 1024px) {
  .calculator-inputs {
    grid-column: span 4;
  }
}

#calculator-form {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xl);
}

section.results {
  display: flex;
  flex-direction: column;
}

@media (min-width: 1024px) {
  section.results {
    grid-column: span 8;
  }
}

/* Form Elements */
.input-group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.input-group-divider {
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--border-colour);
}

.input-label {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

.input-wrapper {
  position: relative;
}

.input-prefix {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-secondary);
  font-weight: 500;
}

input[type="number"],
select {
  width: 100%;
  padding: var(--spacing-md) var(--spacing-lg);
  background-color: var(--bg-input);
  border: 2px solid var(--border-input);
  border-radius: var(--border-radius-xl);
  font-size: 1.125rem;
  font-weight: 700;
  transition: border-colour var(--transition-speed);
  outline: none;
  color: var(--text-main);
}

input[type="number"].pl-10 {
  padding-left: 2.5rem;
}

input[type="number"]:focus,
select:focus {
  border-color: var(--primary-colour);
}

button[type="reset"] {
  background: none;
  border: 2px solid var(--border-colour);
  border-radius: var(--border-radius-xl);
  padding: var(--spacing-md) var(--spacing-lg);
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--text-muted);
  cursor: pointer;
  transition: all var(--transition-speed);
  margin-top: var(--spacing-md);
  width: 100%;
}

button[type="reset"]:hover {
  background-color: var(--bg-subtle);
  border-color: var(--primary-colour);
  color: var(--primary-colour);
}

button[type="reset"]:focus {
  outline: none;
  border-color: var(--primary-colour);
}

/* Range Inputs (not used but kept minimal) */
.range-group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

/* Results Box */
.results-card {
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-colour);
  border-radius: var(--border-radius-3xl);
  padding: var(--spacing-2xl);
  height: 100%;
  min-height: 350px;
  display: flex;
  flex-direction: column;
}

@media (min-width: 1024px) {
  .results-card {
    padding: var(--spacing-2xl) 3rem;
  }
}

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

.results-label {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-secondary);
  border-bottom: 2px solid var(--border-colour);
  padding-bottom: var(--spacing-xs);
}

.results-summary {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
}

.summary-value-wrapper {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.copy-btn {
  background: none;
  border: 1px solid var(--border-colour);
  border-radius: var(--border-radius-sm);
  padding: 4px;
  cursor: pointer;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-speed);
}

.copy-btn:hover {
  background-color: var(--bg-main);
  color: var(--primary-colour);
  border-color: var(--primary-colour);
}

.copy-btn.copied {
  color: var(--accent-colour);
  border-color: var(--accent-colour);
}

.summary-label {
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.summary-value {
  font-size: 2.25rem;
  font-weight: 900;
  color: var(--primary-colour);
}

/* Grid lines (not used) */
.grid-lines {
  display: none;
}

/* Footer */
footer {
  margin-top: 4rem;
  padding-top: var(--spacing-xl);
  border-top: 1px solid var(--border-colour);
  display: flex;
  justify-content: center;
  align-items: center;
  color: var(--text-secondary);
  font-size: 0.75rem;
  font-weight: 500;
  text-align: center;
}

footer p {
  max-width: 600px;
}

/* Custom Select Arrow */
select {
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%2364748b' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
  background-position: right 0.5rem center;
  background-repeat: no-repeat;
  background-size: 1.5em 1.5em;
  padding-right: 2.5rem;
  appearance: none;
}

[data-theme="dark"] select {
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%2394a3b8' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
}

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

/* Toast Notification */
.toast-container {
  position: fixed;
  top: 2rem;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1000;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
  pointer-events: none;
}

.toast {
  background-color: var(--primary-colour);
  color: var(--bg-main);
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--border-radius-lg);
  font-weight: 600;
  font-size: 0.875rem;
  box-shadow: var(--shadow-md);
  opacity: 0;
  transform: translateY(-1rem);
  transition: all 0.3s ease;
  pointer-events: auto;
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  white-space: nowrap;
}

.toast.show {
  opacity: 1;
  transform: translateY(0);
}

.toast.fade-out {
  opacity: 0;
  transform: translateY(-1rem);
}