:root {
  /* Brand (Light) */
  --accent: #2563eb;
  --accent-2: #1d4ed8;

  --bg: #f6f7fb;
  --surface: rgba(255, 255, 255, 0.9);
  --surface-solid: #ffffff;

  --text: #0f172a;
  --muted: #64748b;

  --border: rgba(15, 23, 42, 0.08);

  --success: #16a34a;
  --warning: #f59e0b;
  --danger: #ef4444;

  --radius: 14px;
  --shadow: 0 16px 40px rgba(2, 6, 23, 0.08);
  --shadow-sm: 0 8px 20px rgba(2, 6, 23, 0.06);

  --font: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  --max: 1120px;
}

/* ✅ Auto Dark Mode */
@media (prefers-color-scheme: dark) {
  :root {
    --accent: #38bdf8;
    --accent-2: #0ea5e9;

    --bg: #070a12;
    --surface: rgba(2, 6, 23, 0.78);
    --surface-solid: #020617;

    --text: #e5e7eb;
    --muted: #94a3b8;

    --border: rgba(148, 163, 184, 0.16);

    --success: #22c55e;
    --warning: #facc15;
    --danger: #fb7185;

    --shadow: 0 18px 48px rgba(0, 0, 0, 0.55);
    --shadow-sm: 0 10px 26px rgba(0, 0, 0, 0.35);
  }
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: var(--font);
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 20% -10%, rgba(37, 99, 235, 0.18), transparent 60%),
    radial-gradient(900px 500px at 100% 0%, rgba(56, 189, 248, 0.14), transparent 55%),
    linear-gradient(180deg, var(--bg), var(--bg));
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.app-container { min-height: 100vh; display: flex; flex-direction: column; }

.app-header {
  position: relative;
  padding: 2.2rem 1rem 1.8rem;
  border-bottom: 1px solid var(--border);
}

.header-content { max-width: var(--max); margin: 0 auto; }

.app-title {
  font-size: 2.2rem;
  font-weight: 750;
  letter-spacing: -0.02em;
}

.app-subtitle {
  margin-top: 0.35rem;
  color: var(--muted);
  font-weight: 500;
}

.app-main {
  flex: 1;
  width: 100%;
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.6rem 1rem 2.2rem;
  display: grid;
  grid-template-columns: 420px 1fr;
  gap: 1.2rem;
}

@media (max-width: 980px) { .app-main { grid-template-columns: 1fr; } }

.form-section, .posts-section { width: 100%; }

.section-header { padding: 0.6rem 0.2rem 1rem; }

.section-header h2 {
  font-size: 1.35rem;
  letter-spacing: -0.01em;
}

.section-description {
  color: var(--muted);
  margin-top: 0.25rem;
  font-size: 0.95rem;
}

/* Cards */
.form-container,
.post-card,
.loading-indicator,
.no-posts,
.modal-content {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(10px);
}

/* Form */
.form-container { padding: 1.1rem; }

.post-form { max-width: 100%; }

.form-group { margin-bottom: 0.9rem; }

.form-group label {
  display: block;
  font-weight: 650;
  margin-bottom: 0.35rem;
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 0.8rem 0.85rem;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--surface-solid);
  color: var(--text);
  outline: none;
  transition: border-color .12s ease, box-shadow .12s ease;
}

.form-group textarea { min-height: 140px; resize: vertical; }

.form-group input:focus,
.form-group textarea:focus {
  border-color: rgba(56, 189, 248, 0.6);
  box-shadow: 0 0 0 4px rgba(56, 189, 248, 0.12);
}

.field-error { color: var(--danger); font-size: 0.85rem; margin-top: 0.3rem; }

.form-actions { display: flex; gap: 0.6rem; align-items: center; }

/* Buttons */
.btn {
  border: 0;
  border-radius: 12px;
  padding: 0.78rem 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform .12s ease, filter .12s ease;
  box-shadow: var(--shadow-sm);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  user-select: none;
}

.btn:active { transform: translateY(1px); }

.btn-primary {
  color: #001018;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
}

.btn-secondary,
.btn-cancel {
  color: var(--text);
  background: rgba(148, 163, 184, 0.14);
  border: 1px solid var(--border);
}

.btn-edit {
  color: #001018;
  background: linear-gradient(135deg, #fbbf24, #f59e0b);
  padding: 0.55rem 0.8rem;
  font-size: 0.9rem;
}

.btn-delete {
  color: #001018;
  background: linear-gradient(135deg, #fb7185, #ef4444);
  padding: 0.55rem 0.8rem;
  font-size: 0.9rem;
}

@media (max-width: 520px) {
  .form-actions { flex-direction: column; }
  .btn { width: 100%; }
}

/* Posts */
.posts-container { display: grid; gap: 0.9rem; }

.post-card {
  padding: 1.1rem;
  transition: transform .14s ease, box-shadow .14s ease;
}

.post-card:hover { transform: translateY(-2px); box-shadow: var(--shadow); }

.post-header {
  display: flex;
  justify-content: space-between;
  gap: 0.8rem;
  flex-wrap: wrap;
  align-items: flex-start;
}

.post-title {
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.post-meta {
  color: var(--muted);
  font-size: 0.85rem;
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.post-content {
  margin-top: 0.7rem;
  color: var(--text);
  white-space: pre-wrap;
}

.post-actions {
  margin-top: 0.9rem;
  display: flex;
  gap: 0.55rem;
  justify-content: flex-end;
}

/* Loading */
.loading-indicator { padding: 1.2rem; text-align: center; }
.loading-spinner {
  width: 38px; height: 38px;
  border-radius: 50%;
  border: 3px solid rgba(148,163,184,.25);
  border-top-color: var(--accent);
  margin: 0.2rem auto 0.8rem;
  animation: spin 1s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* Errors / success */
.error-container { margin-bottom: 1rem; }

.error-message {
  background: rgba(239, 68, 68, 0.08);
  border: 1px solid rgba(239, 68, 68, 0.35);
  border-radius: var(--radius);
  padding: 0.9rem;
  color: var(--text);
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
}

.success-message {
  position: fixed;
  top: 18px;
  right: 18px;
  z-index: 9999;
  background: rgba(34, 197, 94, 0.10);
  border: 1px solid rgba(34, 197, 94, 0.35);
  border-radius: 14px;
  padding: 0.85rem 1rem;
  box-shadow: var(--shadow);
}

/* Modals */
.modal {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(2, 6, 23, 0.65);
  padding: 1rem;
  z-index: 1000;
}

.modal-content {
  width: min(860px, 100%);
  max-height: 86vh;
  overflow: auto;
  padding: 1.2rem;
}

.close {
  float: right;
  font-size: 2rem;
  color: var(--muted);
  cursor: pointer;
}

/* Floating button */
.educational-btn {
  position: fixed;
  right: 18px;
  bottom: 18px;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: rgba(148, 163, 184, 0.14);
  color: var(--text);
  box-shadow: var(--shadow);
  cursor: pointer;
}
.educational-btn:hover { filter: brightness(1.05); }