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

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: radial-gradient(ellipse at center, #092f40 0%, #0f1218 100%);
  color: #f5f2f2;
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
}

/* Date & Time */
.date-time {
  position: absolute;
  top: 20px;
  left: 30px;
  font-size: 14px;
  font-family: 'Courier New', Courier, monospace;
  color: #00ffff;
  opacity: 0.8;
}

/* Popup Instruction */
.instruction-popup {
  position: absolute;
  top: 30px;
  right: 30px;
  background: rgba(30, 30, 30, 0.7);
  padding: 15px;
  border-radius: 10px;
  font-size: 13px;
  line-height: 1.5;
  max-width: 200px;
  box-shadow: 0 0 15px rgba(0,255,255,0.1);
  z-index: 100;
}

.instruction-popup button {
  margin-top: 8px;
  padding: 6px 12px;
  border: none;
  border-radius: 6px;
  background: #00ffff;
  color: #0d1117;
  font-weight: bold;
  cursor: pointer;
}

.instruction-popup button:hover {
  background: #174255;
}

/* Container */
.container {
  max-width: 600px;
  margin: 100px auto;
  background: rgba(20, 20, 30, 0.7);
  padding: 30px;
  border-radius: 16px;
  backdrop-filter: blur(6px);
  box-shadow: 0 0 20px rgba(0,255,255,0.05);
}

header h1 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 10px;
  color: #8cd6de;
  text-shadow: 0 0 10px #00ffff33;
}

header h3 {
  text-align: center;
  font-size: 1rem;
  margin-bottom: 20px;
  font-weight: normal;
  color: #999;
}

/* Input */
.input {
  width: 100%;
  padding: 15px;
  font-size: 16px;
  background: #1e222f;
  border: none;
  border-radius: 10px;
  color: #9f5656;
  margin-bottom: 20px;
  outline: none;
}

/* Todos */
.todos {
  list-style: none;
}

.todos li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: #2b2f3e;
  padding: 10px 16px;
  border-radius: 8px;
  margin-bottom: 10px;
  transition: background 0.2s ease-in-out;
}

.todos li:hover {
  background: #353b4d;
}

.todos li.completed span {
  text-decoration: line-through;
  color: #aaa;
}

.todos input[type="checkbox"] {
  margin-right: 12px;
  transform: scale(1.2);
  cursor: pointer;
}

/* Footer */
footer {
  position: fixed;
  bottom: 20px;
  width: 100%;
  text-align: center;
  color: #888;
  font-family: 'Cursive', sans-serif;
  font-size: 0.9rem;
  letter-spacing: 1px;
}

footer span {
  color: red;
}