/* Theming tokens (light defaults) */
:root {
  --bg-gradient-start: #eaf4ff;
  --bg-gradient-end: #f8fafc;
  --text: #0b0b0c;

  --header-bg: #0b6bc6;
  --header-fg: #ffffff;

  --card-bg: #ffffff;
  --card-border: #e5e7eb;
  --card-shadow: 0 10px 30px rgba(15, 23, 42, 0.10);

  --h1-color: #0c4a6e;
  --intro-color: #556070;

  --input-bg: #ffffff;
  --input-fg: #111827;
  --input-border: #cbd5e1;
  --input-focus-border: #2563eb;
  --input-focus-glow: rgba(37, 99, 235, 0.35);
  --input-focus-bg: #f0f9ff;

  --btn-primary-fg: #ffffff;
  --btn-primary-start: #2563eb;
  --btn-primary-end: #3b82f6;
  --btn-primary-hover-start: #1e40af;
  --btn-primary-hover-end: #2563eb;
  --btn-primary-shadow: 0 8px 18px rgba(37, 99, 235, 0.35);

  --output-bg: #ecfdf5;
  --output-fg: #065f46;
  --output-border: #bbf7d0;

  --copy-btn-bg: #10b981;
  --copy-btn-fg: #ffffff;
  --copy-btn-hover-bg: #059669;

  --footer-bg: #f1f5f9;
  --footer-fg: #64748b;
  --link-color: #2563eb;

  --radius: 14px;
}

/* System dark default if no user choice is set */
@media (prefers-color-scheme: dark) {
  :root {
    --bg-gradient-start: #0b0b0c;
    --bg-gradient-end: #101317;
    --text: #e5e7eb;

    --header-bg: #0a436e;
    --header-fg: #e5e7eb;

    --card-bg: #0f172a;
    --card-border: #1f2937;
    --card-shadow: 0 0 0 rgba(0,0,0,0);

    --h1-color: #93c5fd;
    --intro-color: #9aa2ad;

    --input-bg: #111827;
    --input-fg: #e5e7eb;
    --input-border: #374151;
    --input-focus-border: #60a5fa;
    --input-focus-glow: rgba(96,165,250,0.45);
    --input-focus-bg: #0f172a;

    --btn-primary-fg: #ffffff;
    --btn-primary-start: #1d4ed8;
    --btn-primary-end: #2563eb;
    --btn-primary-hover-start: #1e3a8a;
    --btn-primary-hover-end: #1d4ed8;
    --btn-primary-shadow: 0 0 0 rgba(0,0,0,0);

    --output-bg: #0b2e24;
    --output-fg: #a7f3d0;
    --output-border: #14532d;

    --copy-btn-bg: #10b981;
    --copy-btn-fg: #ffffff;
    --copy-btn-hover-bg: #059669;

    --footer-bg: #0b1220;
    --footer-fg: #9aa2ad;
    --link-color: #60a5fa;
  }
}

/* Explicit overrides from the toggle (populated) */
:root[data-theme="light"] {
  --bg-gradient-start: #eaf4ff;
  --bg-gradient-end: #f8fafc;
  --text: #0b0b0c;

  --header-bg: #0b6bc6;
  --header-fg: #ffffff;

  --card-bg: #ffffff;
  --card-border: #e5e7eb;
  --card-shadow: 0 10px 30px rgba(15, 23, 42, 0.10);

  --h1-color: #0c4a6e;
  --intro-color: #556070;

  --input-bg: #ffffff;
  --input-fg: #111827;
  --input-border: #cbd5e1;
  --input-focus-border: #2563eb;
  --input-focus-glow: rgba(37, 99, 235, 0.35);
  --input-focus-bg: #f0f9ff;

  --btn-primary-fg: #ffffff;
  --btn-primary-start: #2563eb;
  --btn-primary-end: #3b82f6;
  --btn-primary-hover-start: #1e40af;
  --btn-primary-hover-end: #2563eb;
  --btn-primary-shadow: 0 8px 18px rgba(37, 99, 235, 0.35);

  --output-bg: #ecfdf5;
  --output-fg: #065f46;
  --output-border: #bbf7d0;

  --copy-btn-bg: #10b981;
  --copy-btn-fg: #ffffff;
  --copy-btn-hover-bg: #059669;

  --footer-bg: #f1f5f9;
  --footer-fg: #64748b;
  --link-color: #2563eb;

  --radius: 14px;
}

:root[data-theme="dark"] {
  --bg-gradient-start: #0b0b0c;
  --bg-gradient-end: #101317;
  --text: #e5e7eb;

  --header-bg: #0a436e;
  --header-fg: #e5e7eb;

  --card-bg: #0f172a;
  --card-border: #1f2937;
  --card-shadow: 0 0 0 rgba(0,0,0,0);

  --h1-color: #93c5fd;
  --intro-color: #9aa2ad;

  --input-bg: #111827;
  --input-fg: #e5e7eb;
  --input-border: #374151;
  --input-focus-border: #60a5fa;
  --input-focus-glow: rgba(96,165,250,0.45);
  --input-focus-bg: #0f172a;

  --btn-primary-fg: #ffffff;
  --btn-primary-start: #1d4ed8;
  --btn-primary-end: #2563eb;
  --btn-primary-hover-start: #1e3a8a;
  --btn-primary-hover-end: #1d4ed8;
  --btn-primary-shadow: 0 0 0 rgba(0,0,0,0);

  --output-bg: #0b2e24;
  --output-fg: #a7f3d0;
  --output-border: #14532d;

  --copy-btn-bg: #10b981;
  --copy-btn-fg: #ffffff;
  --copy-btn-hover-bg: #059669;

  --footer-bg: #0b1220;
  --footer-fg: #9aa2ad;
  --link-color: #60a5fa;

  --radius: 14px;
}

/* Base */
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background:
    radial-gradient(1200px 800px at 15% -10%, var(--bg-gradient-start), transparent 60%),
    radial-gradient(1200px 800px at 85% 110%, var(--bg-gradient-start), transparent 55%),
    linear-gradient(135deg, var(--bg-gradient-start) 0%, var(--bg-gradient-end) 100%);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
header {
  position: relative;
  background: var(--header-bg);
  color: var(--header-fg);
  padding: 12px 56px 12px 20px;
  font-weight: 700;
  font-size: 1.15rem;
  text-align: center;
  border-bottom: 1px solid rgba(255,255,255,0.08);
  box-shadow: 0 4px 16px rgba(0,0,0,0.15);
}

/* Theme toggle */
.theme-toggle {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  background: transparent;
  color: var(--header-fg);
  border: 1px solid rgba(255,255,255,0.3);
  padding: 6px 10px;
  border-radius: 999px;
  font-size: 0.95rem;
  cursor: pointer;
  line-height: 1;
  transition: background-color .15s ease, border-color .15s ease, transform .04s ease;
}
.theme-toggle:hover { background: rgba(255,255,255,0.1); }
.theme-toggle:active { transform: translateY(calc(-50% + 1px)); }
.theme-toggle:focus { outline: 2px solid rgba(255,255,255,0.6); outline-offset: 2px; }

/* Card */
main {
  margin: 36px auto;
  width: min(640px, calc(100% - 32px));
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  padding: 28px 28px 26px;
}
h1 {
  margin: 0 0 8px 0;
  font-weight: 800;
  font-size: 1.6rem;
  letter-spacing: -0.01em;
  color: var(--h1-color);
  text-align: center;
}
p.intro {
  margin: 0;
  font-weight: 500;
  font-size: 0.98rem;
  text-align: center;
  color: var(--intro-color);
}

/* Inputs */
.input-group {
  margin-top: 22px;
  display: flex;
  gap: 12px;
  justify-content: center;
}
input[type=number] {
  flex: 1 1 340px;
  font-size: 1.1rem;
  padding: 12px 14px;
  color: var(--input-fg);
  background: var(--input-bg);
  border: 1.5px solid var(--input-border);
  border-radius: 10px;
  transition: border-color .2s ease, box-shadow .2s ease, background-color .2s ease, color .2s ease;
}
input[type=number]:focus {
  outline: none;
  border-color: var(--input-focus-border);
  box-shadow: 0 0 0 4px var(--input-focus-glow);
  background-color: var(--input-focus-bg);
}

/* Primary button */
button#calcBtn {
  background: linear-gradient(135deg, var(--btn-primary-start), var(--btn-primary-end));
  color: var(--btn-primary-fg);
  border: none;
  border-radius: 10px;
  font-weight: 700;
  padding: 0 18px;
  cursor: pointer;
  font-size: 1.05rem;
  box-shadow: var(--btn-primary-shadow);
  transition: filter .18s ease, transform .04s ease, background .2s ease;
  user-select: none;
}
button#calcBtn:hover,
button#calcBtn:focus {
  background: linear-gradient(135deg, var(--btn-primary-hover-start), var(--btn-primary-hover-end));
  outline: none;
  filter: brightness(0.98);
}
button#calcBtn:active { transform: translateY(1px); }

/* Output: button fixed at right, text wraps on the left */
.output-container {
  margin-top: 26px;
  background: var(--output-bg);
  border: 1px dashed var(--output-border);
  border-radius: 12px;
  padding: 14px 16px;
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: start;
  column-gap: 12px;
  font: 600 1.1rem/1.35 ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  color: var(--output-fg);
  user-select: text;
  overflow-wrap: anywhere; /* ensure long text breaks nicely */
}
.output-container #resultText {
  min-width: 0; /* allow wrapping within the grid cell */
}
.output-container #copyBtn {
  place-self: start end; /* top-right corner */
  white-space: nowrap;   /* keep button on a single line */
}

.output-container.flash { animation: pop .35s ease; }
@keyframes pop {
  0%   { transform: scale(0.995); }
  50%  { transform: scale(1.01); }
  100% { transform: scale(1); }
}

/* Copy button */
button#copyBtn {
  border: none;
  background: var(--copy-btn-bg);
  padding: 8px 14px;
  border-radius: 10px;
  box-shadow: 0 4px 10px rgba(16,185,129,0.35);
  color: var(--copy-btn-fg);
  cursor: pointer;
  font-weight: 800;
  font-size: 0.98rem;
  transition: background .2s ease, transform .04s ease, filter .18s ease;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  user-select: none;
}
button#copyBtn:hover,
button#copyBtn:focus {
  background: var(--copy-btn-hover-bg);
  outline: none;
  filter: brightness(0.98);
}
button#copyBtn:active { transform: translateY(1px); }

/* Clipboard icon */
.copy-icon { width: 18px; height: 18px; fill: currentColor; }

/* Footer */
footer {
  margin-top: auto;
  padding: 18px 20px;
  font-size: 0.9rem;
  text-align: center;
  color: var(--footer-fg);
  background: var(--footer-bg);
  border-top: 1px solid var(--card-border);
  user-select: none;
}
footer a { color: var(--link-color); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* Responsive */
@media (max-width: 480px) {
  main { width: calc(100% - 20px); padding: 20px; }
  .input-group { flex-wrap: wrap; }
  button#calcBtn { width: 100%; height: 44px; }
}