:root {
    --bg-color: #f4f7f6;
    --card-bg: #ffffff;
    --text-color: #333333;
    --primary-color: #4a90e2;
    --border-radius: 8px;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 0;
}

header {
    background-color: var(--primary-color);
    color: white;
    text-align: center;
    padding: 2rem 1rem;
}

.container {
    max-width: 1000px;
    margin: 2rem auto;
    padding: 0 1rem;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.card {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}

h2 {
    margin-top: 0;
    color: #444;
    border-bottom: 2px solid var(--bg-color);
    padding-bottom: 0.5rem;
}

ul {
    list-style: none;
    padding: 0;
}

li {
    margin: 0.8rem 0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.input-group {
    display: flex;
    gap: 0.5rem;
    margin-top: 1rem;
}

.button-group {
    display: flex;
    gap: 0.5rem;
    margin-top: 1rem;
    justify-content: center;
}

input[type="text"], input[type="date"], textarea {
    width: 100%;
    padding: 0.5rem;
    border: 1px solid #ccc;
    border-radius: 4px;
}

textarea {
    height: 150px;
    resize: vertical;
}

button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    cursor: pointer;
    font-weight: bold;
}

button:hover {
    opacity: 0.9;
}

.btn-secondary {
    background-color: #e0e0e0;
    color: #333;
}

.timer-display {
    font-size: 3rem;
    font-weight: bold;
    text-align: center;
    margin: 1rem 0;
    font-variant-numeric: tabular-nums;
    color: var(--primary-color);
}

.countdown-display {
    font-size: 1.25rem;
    font-weight: bold;
    text-align: center;
    margin: 1.5rem 0;
    color: #e67e22;
}

/* Flashcard Styles */
.flashcard {
    background: #f9f9f9;
    border: 2px dashed var(--primary-color);
    height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    cursor: pointer;
    border-radius: var(--border-radius);
    padding: 1rem;
    font-weight: bold;
}
.flashcard.flipped .front { display: none; }
.flashcard:not(.flipped) .back { display: none; }
.hint { font-size: 0.85rem; color: #666; text-align: center; margin-top: 0.5rem; }