/* Global Styles */
:root {
    --primary-color: #3498db;
    --secondary-color: #2ecc71;
    --background-color: #f5f5f5;
    --card-background: #ffffff;
    --card-back-background: #e8f4fd;
    --text-color: #333333;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    --transition-speed: 0.6s;
}

.dark-mode {
    --primary-color: #2980b9;
    --secondary-color: #27ae60;
    --background-color: #1a1a1a;
    --card-background: #2c2c2c;
    --card-back-background: #3d3d3d;
    --text-color: #f0f0f0;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
}

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

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

/* Header Styles */
header {
    text-align: center;
    margin-bottom: 30px;
}

h1 {
    color: var(--primary-color);
    margin-bottom: 15px;
    font-size: 2.5rem;
}

.controls {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 20px;
    flex-wrap: wrap;
    margin-bottom: 30px;
}

#search-bar {
    padding: 12px 20px;
    border-radius: 30px;
    border: 1px solid #ddd;
    width: 100%;
    max-width: 400px;
    font-size: 16px;
    background-color: var(--card-background);
    color: var(--text-color);
    transition: all 0.3s;
}

#search-bar:focus {
    outline: none;
    box-shadow: 0 0 0 2px var(--primary-color);
}

.button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 30px;
    cursor: pointer;
    font-size: 16px;
    transition: all 0.3s;
}

.button:hover {
    background-color: var(--secondary-color);
    transform: scale(1.05);
}

.button.active {
    background-color: var(--secondary-color);
}

/* Flashcard Container */
.flashcards-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 25px;
    max-width: 1200px;
    margin: 0 auto;
}

.shuffle-mode .flashcards-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 300px;
}

.no-cards-message {
    text-align: center;
    grid-column: 1 / -1;
    padding: 40px;
    font-size: 1.2rem;
    color: var(--text-color);
}

/* Flashcard Styles */
.flashcard {
    perspective: 1000px;
    height: 200px;
    cursor: pointer;
}

.shuffle-mode .flashcard {
    width: 90%;
    max-width: 400px;
}

.flashcard-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform var(--transition-speed) ease-in-out;
    transform-style: preserve-3d;
    border-radius: 15px;
    box-shadow: var(--shadow);
}

.flashcard:hover .flashcard-inner {
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
}

.flashcard.flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-front, .flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 15px;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.flashcard-front {
    background-color: var(--card-background);
    color: var(--text-color);
}

.flashcard-back {
    background-color: var(--card-back-background);
    color: var(--text-color);
    transform: rotateY(180deg);
}

.word {
    font-size: 24px;
    font-weight: bold;
}

.definition {
    font-size: 16px;
    line-height: 1.5;
    overflow-y: auto;
    max-height: 160px;
}

/* Progress indicator for shuffle mode */
.progress-indicator {
    display: none;
    text-align: center;
    margin-top: 20px;
    font-size: 16px;
}

.shuffle-mode .progress-indicator {
    display: block;
}

/* Loading state */
.loading {
    text-align: center;
    padding: 40px;
    font-size: 1.2rem;
    color: var(--text-color);
    grid-column: 1 / -1;
}

/* Mobile View */
@media (max-width: 768px) {
    .flashcards-container {
        display: flex;
        flex-direction: column;
        align-items: center;
    }

    .flashcard {
        width: 90%;
        max-width: 320px;
        margin-bottom: 20px;
    }

    h1 {
        font-size: 2rem;
    }

    .controls {
        flex-direction: column;
    }
}