static/style.css

/* ===================================================================
   GridLens — dark cyan theme
   Tokens are declared as CSS variables so the palette stays consistent
   and easy to retune from one place.
   =================================================================== */

:root {
  /* color */
  --bg: #061619;
  --surface: #0C2429;
  --surface-raised: #103138;
  --surface-hover: #163C44;
  --border: #1D4A50;
  --border-strong: #2C6168;
  --cyan: #34D6C6;
  --cyan-soft: rgba(52, 214, 198, 0.12);
  --cyan-dim: #1B8C81;
  --ink: #EAF6F4;
  --ink-dim: #82ACAC;
  --ink-faint: #4F7478;
  --error: #E8765A;
  --error-soft: rgba(232, 118, 90, 0.12);

  /* type */
  --font-display: 'Space Grotesk', sans-serif;
  --font-body: 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
}

* { box-sizing: border-box; }

/* The browser's default [hidden] rule has the same specificity as a
   single class selector, so without this, rules like ".result { display:
   grid }" further down the sheet can silently override the hidden
   attribute and show a section before it should appear. */
[hidden] { display: none !important; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background:
    repeating-linear-gradient(0deg, rgba(52,214,198,0.035) 0 1px, transparent 1px 64px),
    repeating-linear-gradient(90deg, rgba(52,214,198,0.035) 0 1px, transparent 1px 64px),
    var(--bg);
  color: var(--ink);
  font-family: var(--font-body);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--cyan); }

:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ---------- header ---------- */

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 28px 48px 0;
  flex-wrap: wrap;
  gap: 8px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-grid {
  display: grid;
  grid-template-columns: repeat(3, 6px);
  grid-template-rows: repeat(3, 6px);
  gap: 2px;
}

.logo-grid span {
  background: var(--border-strong);
  border-radius: 1px;
}

.logo-grid span.lit {
  background: var(--cyan);
}

@media (prefers-reduced-motion: no-preference) {
  .logo-grid span.lit {
    animation: pulse 2.4s ease-in-out infinite;
  }
}

@keyframes pulse {
  0%, 100% { opacity: 1; box-shadow: 0 0 0 0 var(--cyan-soft); }
  50% { opacity: 0.55; box-shadow: 0 0 6px 2px var(--cyan-soft); }
}

.logo-text {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 20px;
  letter-spacing: -0.02em;
}

.header-note {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink-faint);
  letter-spacing: 0.02em;
}

/* ---------- hero ---------- */

main {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 48px;
}

.hero {
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 56px;
  align-items: center;
  padding: 56px 0 40px;
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--cyan-dim);
  letter-spacing: 0.04em;
  margin: 0 0 18px;
}

.hero-copy h1 {
  font-family: var(--font-display);
  font-size: clamp(42px, 6vw, 64px);
  line-height: 1.02;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 22px;
}

.hero-copy h1 .accent { color: var(--cyan); }

.lede {
  font-size: 16px;
  color: var(--ink-dim);
  max-width: 36ch;
  margin: 0;
}

/* ---------- dropzone (signature element) ---------- */

.dropzone {
  position: relative;
  aspect-ratio: 1 / 1;
  border: 1px dashed var(--border-strong);
  border-radius: 10px;
  background: var(--surface);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  overflow: hidden;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.dropzone:hover,
.dropzone.drag-over {
  background: var(--surface-raised);
  border-color: var(--cyan-dim);
}

.bracket {
  position: absolute;
  width: 22px;
  height: 22px;
  border: 2px solid var(--cyan);
  opacity: 0.85;
}

.bracket-tl { top: 10px; left: 10px; border-right: none; border-bottom: none; }
.bracket-tr { top: 10px; right: 10px; border-left: none; border-bottom: none; }
.bracket-bl { bottom: 10px; left: 10px; border-right: none; border-top: none; }
.bracket-br { bottom: 10px; right: 10px; border-left: none; border-top: none; }

.scanline {
  position: absolute;
  left: 8px;
  right: 8px;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--cyan), transparent);
  top: 10%;
  opacity: 0;
}

@media (prefers-reduced-motion: no-preference) {
  .dropzone:hover .scanline,
  .dropzone.drag-over .scanline {
    opacity: 1;
    animation: sweep 1.6s ease-in-out infinite;
  }
}

@keyframes sweep {
  0%   { top: 10%; }
  50%  { top: 88%; }
  100% { top: 10%; }
}

.dropzone-empty {
  text-align: center;
  color: var(--ink-dim);
  padding: 24px;
}

.dropzone-empty svg { color: var(--cyan-dim); margin-bottom: 10px; }

.dz-title {
  font-family: var(--font-display);
  font-weight: 600;
  color: var(--ink);
  margin: 0 0 4px;
  font-size: 16px;
}

.dz-sub {
  margin: 0;
  font-size: 13px;
  color: var(--ink-faint);
}

.dropzone-preview {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* ---------- buttons ---------- */

.upload-actions {
  display: flex;
  gap: 12px;
  margin-top: 16px;
  align-items: center;
  flex-wrap: wrap;
}

.btn {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 14px;
  border-radius: 7px;
  padding: 11px 20px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, opacity 0.15s ease;
}

.btn-primary {
  background: var(--cyan);
  color: #04211E;
  margin-left: auto;
}

.btn-primary:hover:not(:disabled) { background: #4EE2D2; }

.btn-primary:disabled {
  background: var(--surface-raised);
  color: var(--ink-faint);
  cursor: not-allowed;
}

.btn-ghost {
  background: transparent;
  color: var(--ink-dim);
  border-color: var(--border-strong);
}

.btn-ghost:hover { color: var(--ink); border-color: var(--cyan-dim); }

.error-msg {
  margin: 14px 0 0;
  font-size: 13px;
  color: var(--error);
  background: var(--error-soft);
  border: 1px solid var(--error);
  border-radius: 6px;
  padding: 10px 14px;
}

/* ---------- pipeline (real sequence, hence the numbering) ---------- */

.pipeline { padding: 8px 0 40px; }

.pipeline-steps {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.step {
  flex: 1;
  padding: 18px 16px;
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 6px;
  color: var(--ink-faint);
  transition: color 0.2s ease;
}

.step:last-child { border-right: none; }

.step-index {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink-faint);
}

.step-label {
  font-size: 14px;
  font-weight: 500;
}

.step.active { color: var(--cyan); }
.step.active .step-index { color: var(--cyan); }
.step.done { color: var(--ink-dim); }
.step.done .step-index { color: var(--cyan-dim); }

@media (prefers-reduced-motion: no-preference) {
  .step.active .step-label { animation: flicker 1s ease-in-out infinite; }
}

@keyframes flicker {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

/* ---------- result ---------- */

.result {
  display: grid;
  grid-template-columns: 0.8fr 1fr;
  gap: 40px;
  padding: 16px 0 64px;
  align-items: start;
}

.result-label {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink-faint);
  letter-spacing: 0.03em;
  margin: 0 0 10px;
  text-transform: uppercase;
}

.result-source img {
  width: 100%;
  border-radius: 8px;
  border: 1px solid var(--border);
}

.sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  background: var(--surface);
  border: 2px solid var(--border-strong);
  border-radius: 6px;
  overflow: hidden;
  width: 100%;
  aspect-ratio: 1 / 1;
}

.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(14px, 2.4vw, 20px);
  color: var(--cyan);
}

.cell.thick-right { border-right: 2px solid var(--border-strong); }
.cell.thick-bottom { border-bottom: 2px solid var(--border-strong); }

.result .btn-ghost {
  grid-column: 1 / -1;
  justify-self: start;
}

/* ---------- footer ---------- */

.site-footer {
  max-width: 1080px;
  margin: 0 auto;
  padding: 24px 48px 48px;
  border-top: 1px solid var(--border);
}

.site-footer p {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink-faint);
  margin: 20px 0 0;
}

/* ---------- responsive ---------- */

@media (max-width: 820px) {
  .site-header, main, .site-footer { padding-left: 24px; padding-right: 24px; }

  .hero {
    grid-template-columns: 1fr;
    padding-top: 36px;
  }

  .hero-upload { order: -1; max-width: 360px; margin: 0 auto; }

  .pipeline-steps { flex-direction: column; }
  .step { border-right: none; border-bottom: 1px solid var(--border); }
  .step:last-child { border-bottom: none; }

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

  .result-source img { max-width: 280px; }
}