/* SECTION: Design Tokens */
:root {
  /* Colors */
  --color-bg-primary: #050816;
  --color-bg-elevated: #0b1020;
  --color-surface: #111827;
  --color-border-subtle: #1f2937;
  --color-text-main: #e5e7eb;
  --color-text-muted: #9ca3af;
  --color-accent: #38bdf8;
  --color-accent-soft: rgba(56, 189, 248, 0.14);
  --color-danger: #fb7185;
  --color-danger-soft: rgba(251, 113, 133, 0.15);

  /* Accent RGB for glows */
  --accent-rgb: 56, 189, 248;

  /* Typography */
  --font-sans: "Space Grotesk", system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", sans-serif;

  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.5rem;

  /* Spacing */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 18px;

  /* Shadows */
  --shadow-soft: 0 18px 45px rgba(15, 23, 42, 0.65);

  /* Transitions */
  --transition-fast: 0.15s ease-out;
  --transition-med: 0.22s ease-out;
}

/* Google Font */
@import url("https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;600;700&display=swap");

/* SECTION: Base Layout */
*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-sans);
  background: radial-gradient(circle at top, #0f172a 0, #020617 40%, #000 100%);
  color: var(--color-text-main);
}

.app {
  position: relative;
  max-width: 960px;
  margin: 0 auto;
  padding: var(--space-10) var(--space-6) var(--space-8);
}

.gradient-mesh {
  background:
    radial-gradient(at 40% 0%, rgba(56, 189, 248, 0.22) 0, transparent 50%),
    radial-gradient(at 0% 60%, rgba(129, 140, 248, 0.28) 0, transparent 55%),
    radial-gradient(at 100% 100%, rgba(248, 113, 113, 0.22) 0, transparent 55%);
}

.grain::before {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  opacity: 0.04;
  mix-blend-mode: soft-light;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 400 400' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='1.2' numOctaves='3' stitchTiles='noStitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='0.5'/%3E%3C/svg%3E");
}

.app::before {
  /* Soft spotlight behind the grid */
  content: "";
  position: absolute;
  inset: 0;
  margin: auto;
  width: 70%;
  max-width: 720px;
  height: 70%;
  background: radial-gradient(circle, rgba(15, 23, 42, 0.4), transparent 65%);
  z-index: -1;
}

/* SECTION: Typography */
h1,
 h2 {
  margin: 0;
  letter-spacing: -0.03em;
}

h1 {
  font-size: clamp(1.9rem, 3vw, 2.3rem);
  font-weight: 600;
}

h2 {
  font-size: var(--text-lg);
  font-weight: 600;
}

.app-header__subtitle {
  margin-top: var(--space-2);
  margin-bottom: 0;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  max-width: 34rem;
}

.app-header__subtitle strong {
  color: #e5e7eb;
}

/* SECTION: Header */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
}

.app-header__badge {
   padding: var(--space-2) var(--space-4);
   border-radius: 999px;
   border: 1px solid rgba(148, 163, 184, 0.5);
   background: radial-gradient(circle at top, rgba(56, 189, 248, 0.28), transparent 60%),
     rgba(15, 23, 42, 0.9);
   font-size: var(--text-xs);
   text-transform: uppercase;
   letter-spacing: 0.12em;
   white-space: nowrap;
   color: #ffffff;
   text-decoration: none;
   cursor: pointer;
   transition: background var(--transition-fast), border-color var(--transition-fast),
     box-shadow var(--transition-fast), transform var(--transition-fast);
 }

 .app-header__badge:hover {
   border-color: rgba(56, 189, 248, 0.9);
   box-shadow: 0 0 0 1px rgba(56, 189, 248, 0.6), 0 10px 30px rgba(8, 47, 73, 0.9);
   transform: translateY(-1px);
 }


.shadow-soft {
  box-shadow: var(--shadow-soft);
}

/* SECTION: Layout Grid */
.layout {
  background: radial-gradient(circle at top left, rgba(56, 189, 248, 0.12), transparent 55%),
    rgba(15, 23, 42, 0.92);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  border: 1px solid rgba(148, 163, 184, 0.28);
  position: relative;
}

.layout__labels {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-4);
  margin-bottom: var(--space-4);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--color-text-muted);
}

.label {
  padding-left: var(--space-1);
}

.label--invoice {
  color: #a5b4fc;
}

.label--fees {
  color: #67e8f9;
}

.label--transaction {
  color: #fca5a5;
}

.label--calculator {
  color: #bbf7d0;
}

.layout__grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4);
}

/* SECTION: Panels */
.panel {
  background: linear-gradient(to bottom right, rgba(15, 23, 42, 0.95), rgba(15, 23, 42, 0.86));
  border-radius: var(--radius-md);
  padding: var(--space-5);
  border: 1px solid rgba(31, 41, 55, 0.9);
  position: relative;
  overflow: hidden;
}

.panel::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: radial-gradient(circle at top, rgba(56, 189, 248, 0.12), transparent 55%);
  opacity: 0;
  transition: opacity var(--transition-med);
  pointer-events: none;
}

.panel:hover::after {
  opacity: 1;
}

.panel h2 {
  margin-bottom: var(--space-4);
}

.panel--invoice h2 {
  color: #c7d2fe;
}

.panel--fees h2 {
  color: #67e8f9;
}

.panel--transaction h2 {
  color: #fecaca;
}

.panel--calculator h2 {
  color: #bbf7d0;
}

/* SECTION: Form Styles */
.field-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.field-group--summary {
  margin-top: var(--space-4);
  padding-top: var(--space-3);
  border-top: 1px dashed rgba(55, 65, 81, 0.9);
}

.field-row {
  display: flex;
  gap: var(--space-4);
}

label {
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--color-text-muted);
}

.field-description {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.input-with-prefix,
.input-with-suffix {
  display: flex;
  align-items: center;
  background-color: rgba(15, 23, 42, 0.85);
  border-radius: var(--radius-sm);
  border: 1px solid rgba(55, 65, 81, 0.95);
  overflow: hidden;
}

.prefix,
.suffix {
  padding: 0 var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

input[type="number"] {
  width: 100%;
  padding: var(--space-3);
  border: none;
  background: transparent;
  color: var(--color-text-main);
  font-size: var(--text-base);
  font-family: inherit;
  outline: none;
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

input[type="number"]:focus-visible {
  outline: none;
}

.input-with-prefix:focus-within,
.input-with-suffix:focus-within {
  border-color: rgba(56, 189, 248, 0.85);
  box-shadow: 0 0 0 1px rgba(56, 189, 248, 0.3);
}

/* SECTION: Summary rows */
.summary-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
}

.summary-row .value {
  font-variant-numeric: tabular-nums;
  font-size: var(--text-base);
  color: var(--color-text-main);
}

.summary-row--emphasis {
  margin-top: var(--space-3);
  padding-top: var(--space-3);
  border-top: 1px dashed rgba(55, 65, 81, 0.9);
}

.summary-row--emphasis .value {
  font-weight: 600;
}

/* Balance coloring, toggled via JS */
.value--zero {
  color: #bbf7d0 !important;
}

.value--positive {
  color: #facc15 !important;
}

.value--negative {
  color: var(--color-danger) !important;
}

/* SECTION: Hints */
.hint {
  margin: 0;
  margin-top: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

/* SECTION: Calculator controls */
.hint-list {
  margin: var(--space-3) 0 var(--space-4);
  padding-left: var(--space-4);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.hint-list li + li {
  margin-top: var(--space-1);
}

.primary-btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: 999px;
  border: 1px solid rgba(55, 65, 81, 0.95);
  background: radial-gradient(circle at top, rgba(15, 23, 42, 0.85), rgba(15, 23, 42, 0.95));
  color: var(--color-text-main);
  font-size: var(--text-sm);
  font-weight: 500;
  cursor: pointer;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast),
    border-color var(--transition-fast), background var(--transition-fast);
  min-height: 44px;
}

.step-btn:hover {
  border-color: rgba(56, 189, 248, 0.7);
  box-shadow: 0 0 0 1px rgba(56, 189, 248, 0.35);
  transform: translateY(-1px);
}

.step-btn:active {
  transform: translateY(0);
  box-shadow: inset 0 2px 4px rgba(15, 23, 42, 0.9);
}

.primary-btn {
  width: 100%;
  margin-top: var(--space-2);
  background: linear-gradient(to right, rgba(56, 189, 248, 0.12), rgba(45, 212, 191, 0.1));
  border-color: rgba(56, 189, 248, 0.9);
  box-shadow: 0 0 0 1px rgba(56, 189, 248, 0.6), 0 10px 35px rgba(8, 47, 73, 0.9);
}

.primary-btn--secondary {
  margin-top: var(--space-2);
  background: transparent;
  border-color: rgba(148, 163, 184, 0.8);
  box-shadow: none;
}

.primary-btn--secondary:hover {
  background: rgba(15, 23, 42, 0.9);
}

.primary-btn:hover {
  background: linear-gradient(to right, rgba(56, 189, 248, 0.2), rgba(45, 212, 191, 0.18));
  transform: translateY(-1px);
}

.primary-btn:active {
  transform: translateY(0);
  box-shadow: inset 0 2px 5px rgba(15, 23, 42, 0.9);
}

button:focus-visible {
  outline: none;
  box-shadow: 0 0 0 2px rgba(15, 23, 42, 1), 0 0 0 4px rgba(56, 189, 248, 0.8);
}

button {
  color: inherit;
}

/* SECTION: Footer */
.app-footer {
   margin-top: var(--space-6);
   font-size: var(--text-xs);
   color: var(--color-text-muted);
   display: flex;
   justify-content: flex-end;
 }

 .app-footer a {
   color: #ffffff;
   text-decoration: none;
   transition: color var(--transition-fast);
 }

 .app-footer a:hover {
   color: var(--color-accent);
 }


/* SECTION: Responsiveness */
@media (max-width: 900px) {
  .app {
    padding-inline: var(--space-4);
  }

  .layout__labels {
    display: none;
  }

  .panel {
    padding: var(--space-4);
  }
}

@media (max-width: 640px) {
  .app {
    padding-inline: var(--space-3);
    padding-top: var(--space-6);
  }

  .app-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .layout {
    padding: var(--space-4);
  }

  .layout__grid {
    grid-template-columns: 1fr;
  }

  .field-row {
    flex-direction: column;
  }
}