:root {
  --bg: #0f172a;
  --surface: #1e293b;
  --surface-hover: #334155;
  --text: #f1f5f9;
  --text-muted: #94a3b8;
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --danger: #ef4444;
  --success: #22c55e;
  --border: #334155;
  --radius: 12px;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.3);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
}

.hidden { display: none !important; }

.screen {
  min-height: 100vh;
}

/* Login */
.login-box {
  max-width: 400px;
  margin: 15vh auto;
  padding: 2.5rem;
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-align: center;
}

.login-box h1 {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.login-box p {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.25rem;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
}

.btn.primary {
  background: var(--primary);
  color: white;
}

.btn.primary:hover {
  background: var(--primary-hover);
}

.btn.ghost {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border);
}

.btn.ghost:hover {
  background: var(--surface-hover);
  color: var(--text);
}

/* Header */
header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 1.5rem;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.header-left h1 {
  font-size: 1.5rem;
}

.user-email {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Main */
main {
  max-width: 640px;
  margin: 0 auto;
  padding: 1.5rem;
}

.add-task {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.add-task input {
  flex: 1;
  padding: 0.75rem 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 1rem;
}

.add-task input:focus {
  outline: none;
  border-color: var(--primary);
}

/* Filters */
.filters {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.filter-btn {
  padding: 0.4rem 0.9rem;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.9rem;
}

.filter-btn.active,
.filter-btn:hover {
  background: var(--surface);
  color: var(--text);
  border-color: var(--primary);
}

/* Task list */
.task-list {
  list-style: none;
}

.task-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.9rem 1rem;
  background: var(--surface);
  border-radius: 8px;
  margin-bottom: 0.5rem;
  transition: background 0.15s;
}

.task-item:hover {
  background: var(--surface-hover);
}

.task-item.done .task-text {
  text-decoration: line-through;
  color: var(--text-muted);
}

.task-checkbox {
  width: 20px;
  height: 20px;
  accent-color: var(--success);
  cursor: pointer;
}

.task-text {
  flex: 1;
  word-break: break-word;
}

.delete-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.2rem;
  cursor: pointer;
  padding: 0.25rem;
  opacity: 0.6;
}

.delete-btn:hover {
  color: var(--danger);
  opacity: 1;
}

.empty-state {
  text-align: center;
  color: var(--text-muted);
  padding: 2rem;
}

/* Mobile */
@media (max-width: 480px) {
  .login-box {
    margin: 10vh 1rem;
    padding: 1.5rem;
  }
  header {
    padding: 0.75rem 1rem;
  }
  main {
    padding: 1rem;
  }
}