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

:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-card: #ffffff;
  --text-primary: #1a1a1a;
  --text-secondary: #6c757d;
  --border-color: #e0e0e0;
  --accent: #6366f1;
  --accent-hover: #4f46e5;
  --shadow: rgba(0, 0, 0, 0.1);
  --task-bg: #f8f9fa;
  --task-hover: #e9ecef;
  --delete-btn: #ef4444;
  --delete-hover: #dc2626;
}

[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #1e293b;
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --border-color: #334155;
  --accent: #818cf8;
  --accent-hover: #6366f1;
  --shadow: rgba(0, 0, 0, 0.3);
  --task-bg: #334155;
  --task-hover: #475569;
  --delete-btn: #f87171;
  --delete-hover: #ef4444;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  transition: background 0.3s ease, color 0.3s ease;
  padding: 20px;
}

.container {
  max-width: 600px;
  margin: 0 auto;
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 30px;
  padding: 20px 0;
}

h1 {
  font-size: 2.5rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-hover) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.theme-toggle {
  position: relative;
  width: 60px;
  height: 30px;
  background: var(--bg-secondary);
  border-radius: 50px;
  border: 2px solid var(--border-color);
  cursor: pointer;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  padding: 0 4px;
}

.theme-toggle:hover {
  transform: scale(1.05);
}

.toggle-slider {
  width: 22px;
  height: 22px;
  background: var(--accent);
  border-radius: 50%;
  transition: transform 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
}

[data-theme="dark"] .toggle-slider {
  transform: translateX(30px);
}

.input-container {
  background: var(--bg-card);
  padding: 25px;
  border-radius: 16px;
  box-shadow: 0 4px 6px var(--shadow);
  margin-bottom: 30px;
  border: 1px solid var(--border-color);
  transition: all 0.3s ease;
}

.input-wrapper {
  display: flex;
  gap: 10px;
}

input[type="text"] {
  flex: 1;
  padding: 14px 18px;
  border: 2px solid var(--border-color);
  border-radius: 12px;
  font-size: 16px;
  background: var(--bg-secondary);
  color: var(--text-primary);
  transition: all 0.3s ease;
  outline: none;
}

input[type="text"]:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

button {
  padding: 14px 28px;
  background: var(--accent);
  color: white;
  border: none;
  border-radius: 12px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
}

button:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

button:active {
  transform: translateY(0);
}

.tasks-container {
  background: var(--bg-card);
  padding: 25px;
  border-radius: 16px;
  box-shadow: 0 4px 6px var(--shadow);
  border: 1px solid var(--border-color);
  min-height: 200px;
}

.tasks-header {
  font-size: 1.3rem;
  font-weight: 600;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.task-list {
  list-style: none;
}

.task-item {
  background: var(--task-bg);
  padding: 16px 20px;
  border-radius: 12px;
  margin-bottom: 12px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: all 0.3s ease;
  border: 1px solid transparent;
  animation: fadeIn 0.3s ease;
}

.task-item:hover {
  background: var(--task-hover);
  border-color: var(--accent);
  transform: translateX(5px);
}

.task-content {
  display: flex;
  align-items: center;
  gap: 12px;
  flex: 1;
}

.task-number {
  background: var(--accent);
  color: white;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 600;
}

.task-text {
  color: var(--text-primary);
  font-size: 16px;
}

.delete-btn {
  background: var(--delete-btn);
  padding: 8px 16px;
  font-size: 14px;
  border-radius: 8px;
  transition: all 0.3s ease;
}

.delete-btn:hover {
  background: var(--delete-hover);
  transform: scale(1.05);
}

.empty-state {
  text-align: center;
  padding: 40px 20px;
  color: var(--text-secondary);
}

.empty-state-icon {
  font-size: 3rem;
  margin-bottom: 15px;
  opacity: 0.5;
}

.empty-state-text {
  font-size: 1.1rem;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}