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

:root {
    --primary-color: #4A90E2;
    --success-color: #5CB85C;
    --warning-color: #F0AD4E;
    --text-color: #333;
    --bg-color: #F5F5F5;
    --card-bg: #FFFFFF;
    --shadow: 0 2px 10px rgba(0,0,0,0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 100%;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.screen {
    display: none;
    width: 100%;
    min-height: 100vh;
}

.screen.active {
    display: flex;
    flex-direction: column;
}

h1 {
    font-size: 2rem;
    margin-bottom: 2rem;
    text-align: center;
    color: var(--primary-color);
}

h2 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

h3 {
    font-size: 1.2rem;
    margin-bottom: 1rem;
}

/* Buttons */
.btn {
    padding: 16px 32px;
    font-size: 1.1rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    min-height: 48px;
    width: 100%;
    max-width: 400px;
    margin: 8px 0;
    transition: transform 0.1s, opacity 0.2s;
    touch-action: manipulation;
}

.btn:active {
    transform: scale(0.98);
    opacity: 0.9;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

.btn-secondary {
    background-color: #6C757D;
    color: white;
}

.btn-success {
    background-color: var(--success-color);
    color: white;
}

.btn-warning {
    background-color: var(--warning-color);
    color: white;
}

/* Instructions */
.instructions {
    background: var(--card-bg);
    padding: 24px;
    border-radius: 12px;
    box-shadow: var(--shadow);
    max-width: 500px;
    width: 100%;
}

.instructions ol {
    margin: 20px 0;
    padding-left: 24px;
}

.instructions li {
    margin: 12px 0;
    font-size: 1.1rem;
}

/* Settings */
.settings-group {
    background: var(--card-bg);
    padding: 20px;
    margin: 12px 0;
    border-radius: 8px;
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 500px;
}

.settings-group label {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 1.1rem;
    cursor: pointer;
}

.settings-group select {
    padding: 12px;
    font-size: 1rem;
    border: 2px solid #ddd;
    border-radius: 6px;
    min-width: 150px;
}

.settings-group input[type="range"] {
    width: 100%;
    height: 8px;
    border-radius: 5px;
    background: #ddd;
    outline: none;
    margin-top: 10px;
    -webkit-appearance: none;
}

.settings-group input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

.settings-group input[type="range"]::-moz-range-thumb {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    border: none;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

.settings-group #sessionSizeValue {
    font-weight: bold;
    color: var(--primary-color);
    font-size: 1.1rem;
    display: inline;
    white-space: nowrap;
}

.settings-group label > span {
    white-space: nowrap;
}

.settings-group input[type="checkbox"] {
    width: 24px;
    height: 24px;
    margin-right: 12px;
}

/* Word Card */
.uebungsrunde-progress {
    text-align: center;
    font-size: 1rem;
    color: #666;
    margin-bottom: 20px;
}

.card-container {
    perspective: 1000px;
    width: 100%;
    max-width: 500px;
    margin: 20px auto;
    min-height: 300px;
    height: 300px;
}

.card {
    position: relative;
    width: 100%;
    height: 100%;
    min-height: 300px;
    transform-style: preserve-3d;
    transition: transform 0.5s;
    cursor: pointer;
    transform-origin: center center;
    will-change: transform;
}

.card.flipped {
    transform: rotateY(180deg);
}

.card-front,
.card-back {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 16px;
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px;
}

.card-front {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    position: relative;
}

.card-hint {
    position: absolute;
    top: 12px;
    left: 12px;
    font-size: 0.85rem;
    background: rgba(255, 255, 255, 0.95);
    color: #333;
    padding: 8px 12px;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    z-index: 1000;
    white-space: nowrap;
    max-width: calc(100% - 24px);
    font-weight: 500;
    display: none;
}

.card-hint.show {
    display: block;
}

.card-back {
    background: var(--card-bg);
    transform: rotateY(180deg);
    flex-direction: column;
    align-items: flex-start;
    justify-content: flex-start;
    overflow-y: auto;
}

.word-display {
    font-size: 4rem;
    font-weight: bold;
    text-align: center;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}

.info-box {
    width: 100%;
}

.info-box h3 {
    margin-bottom: 20px;
    color: var(--primary-color);
}

.checklist {
    list-style: none;
    padding: 0;
}

.checklist li {
    padding: 12px;
    margin: 8px 0;
    background: #f8f9fa;
    border-radius: 6px;
    font-size: 1.1rem;
    border-left: 4px solid var(--primary-color);
}

.checklist li.optional {
    opacity: 0.7;
}

.repeat-toggle {
    margin-top: 20px;
    padding: 16px;
    background: #fff3cd;
    border-radius: 8px;
    border: 2px solid #ffc107;
}

.repeat-toggle label {
    display: flex;
    align-items: center;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
}

.repeat-toggle input[type="checkbox"] {
    width: 24px;
    height: 24px;
    margin-right: 12px;
}

.action-buttons {
    width: 100%;
    max-width: 500px;
    margin-top: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* End Screen */
#endScreen {
    text-align: center;
}

#confetti {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 1000;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.5);
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-content {
    background-color: var(--card-bg);
    padding: 24px;
    border-radius: 12px;
    max-width: 90%;
    width: 100%;
    max-width: 500px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.3);
}

.link-container {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin: 20px 0;
}

.link-container input {
    padding: 12px;
    font-size: 0.9rem;
    border: 2px solid #ddd;
    border-radius: 6px;
    word-break: break-all;
}

/* Confetti Animation */
@keyframes confettiFall {
    to {
        transform: translateY(100vh) translateX(var(--horizontal)) rotate(360deg);
        opacity: 0;
    }
}

/* Tablet and Desktop */
@media (min-width: 768px) {
    .word-display {
        font-size: 5rem;
    }
    
    .card-container {
        min-height: 400px;
    }
    
    .card-front,
    .card-back {
        min-height: 400px;
    }
}

@media (min-width: 1024px) {
    .container {
        padding: 40px;
    }
    
    .link-container {
        flex-direction: row;
    }
    
    .link-container input {
        flex: 1;
    }
}