:root {
    --primary-color: #4F46E5;
    --primary-hover: #4338CA;
    --bg-color: #F3F4F6;
    --card-color: #FFFFFF;
    --text-color: #1F2937;
    --text-secondary: #6B7280;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    min-height: 100vh;
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.container {
    width: 100%;
    max-width: 480px;
    margin: 0 auto;
}

h1 {
    font-size: 1.5rem;
    font-weight: bold;
    margin-bottom: 1.5rem;
    text-align: center;
}

.upload-container {
    width: 100%;
    margin-bottom: 1.5rem;
}

.file-upload {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    padding: 1rem;
    background-color: var(--card-color);
    border: 2px dashed #D1D5DB;
    border-radius: 0.5rem;
    cursor: pointer;
}

.file-upload:hover {
    background-color: #F9FAFB;
}

.file-upload-text {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-left: 0.5rem;
}

.mode-filter {
    width: 100%;
    margin-bottom: 1.5rem;
}

select {
    width: 100%;
    padding: 0.5rem;
    border: 1px solid #D1D5DB;
    border-radius: 0.375rem;
    font-size: 1rem;
}

select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.card {
    width: 100%;
    background-color: var(--card-color);
    border-radius: 0.75rem;
    overflow: hidden;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    margin-bottom: 1.5rem;
    cursor: pointer;
}

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

.card-header h2 {
    font-size: 1.125rem;
    font-weight: 600;
}

.card-body {
    padding: 1.5rem;
}

.card-question {
    text-align: center;
    margin-bottom: 1rem;
    font-size: 1.25rem;
    font-weight: 500;
}

.card-answer {
    margin-top: 1.5rem;
    padding: 1rem;
    background-color: #F3F4F6;
    border-radius: 0.5rem;
    text-align: center;
}

.card-answer p {
    font-size: 1.25rem;
    font-weight: 700;
}

.card-hint {
    margin-top: 1rem;
    text-align: center;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem 1.5rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 0.375rem;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s;
}

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

.btn svg {
    margin-right: 0.5rem;
}

.stats {
    margin-top: 1.5rem;
    text-align: center;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.error-msg {
    color: #DC2626;
    font-size: 0.875rem;
    text-align: center;
    margin-top: 0.5rem;
}

.hidden {
    display: none;
}

.loading {
    text-align: center;
    margin-top: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

@media (max-width: 640px) {
    body {
        padding: 16px;
    }
    
    h1 {
        font-size: 1.3rem;
    }
    
    .card-question {
        font-size: 1.1rem;
    }
    
    .card-answer p {
        font-size: 1.1rem;
    }
}