:root {
  --font-body: "Space Grotesk", "Segoe UI", sans-serif;
  --font-mono: "IBM Plex Mono", "Consolas", monospace;

  --bg-main: radial-gradient(circle at 0% 0%, #f0f7ff 0%, #f7fafc 45%, #eef2f7 100%);
  --bg-card: #ffffff;
  --text-main: #122035;
  --text-muted: #52617a;
  --border: #dbe2ec;
  --accent: #0d6efd;
  --accent-strong: #0a58ca;
  --danger: #c92a2a;
  --danger-bg: #fff1f1;
  --success: #1a7f37;
  --shadow: 0 10px 30px rgba(18, 32, 53, 0.08);
}

html[data-theme="dark"] {
  --bg-main: radial-gradient(circle at 0% 0%, #1f2733 0%, #171d26 45%, #11161e 100%);
  --bg-card: #1f2733;
  --text-main: #e6ecf3;
  --text-muted: #9eb0c9;
  --border: #314054;
  --accent: #67a8ff;
  --accent-strong: #8abaff;
  --danger: #ff8a8a;
  --danger-bg: #382325;
  --success: #7fd69b;
  --shadow: 0 12px 28px rgba(0, 0, 0, 0.35);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-body);
  color: var(--text-main);
  background: var(--bg-main);
}

.app-shell {
  width: min(760px, 92vw);
  margin: 3rem auto;
  display: grid;
  gap: 1rem;
}

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

h1 {
  margin: 0;
  font-size: clamp(1.8rem, 4vw, 2.4rem);
  letter-spacing: 0.04em;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1rem;
  box-shadow: var(--shadow);
}

.todo-form {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.65rem;
}

input[type="text"] {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: transparent;
  color: var(--text-main);
  padding: 0.7rem 0.85rem;
  font: inherit;
}

button {
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #ffffff20;
  color: var(--text-main);
  padding: 0.65rem 0.9rem;
  font: 600 0.9rem var(--font-mono);
  cursor: pointer;
}

button:hover {
  border-color: var(--accent);
  color: var(--accent-strong);
}

#todo-form button {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 12%, transparent);
}

.message {
  min-height: 1.2rem;
  margin: 0.6rem 0 0;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.message.error {
  color: var(--danger);
}

.message.success {
  color: var(--success);
}

.todo-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0.6rem;
}

.todo-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.55rem 0.65rem;
}

.todo-check {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  cursor: pointer;
  min-width: 0;
}

.todo-title {
  overflow-wrap: anywhere;
}

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

.todo-delete {
  border-color: color-mix(in srgb, var(--danger) 35%, var(--border));
  background: var(--danger-bg);
}

.empty-state {
  margin: 0.4rem 0 0;
  color: var(--text-muted);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  border: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
}

@media (max-width: 640px) {
  .app-shell {
    margin: 1rem auto;
  }

  .todo-form {
    grid-template-columns: 1fr;
  }

  .todo-item {
    gap: 0.6rem;
    align-items: flex-start;
    flex-direction: column;
  }
}