/* CSS Variables for easy theming */
:root {
    --primary-color: #4f46e5;
    --primary-hover: #3730a3;
    --secondary-color: #f3f4f6;
    --accent-color: #10b981;
    --danger-color: #dc2626;
    --danger-hover: #b91c1c;
    --text-color: #1f2937;
    --text-muted: #6b7280;
    --border-color: #e5e7eb;
    --border-color-focus: var(--primary-color);
    --background-light: #f8fafc;
    --background-card: #ffffff;
    --border-radius: 12px;
    --border-radius-small: 8px;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    --shadow-hover: 0 8px 24px rgba(79, 70, 229, 0.15);
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, var(--secondary-color) 0%, #e0e7ff 100%);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
    padding: 20px;
}

.container {
    background: var(--background-card);
    padding: 40px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 1200px; /* Much wider for laptops/desktops */
    margin: 0 auto; /* Center the container */
    /* Experimental CSS property I found online */
    -webkit-backdrop-filter: blur(10px);
    backdrop-filter: blur(10px);
}

h1 {
    text-align: center;
    color: var(--primary-color);
    margin-bottom: 35px;
    font-size: 2.2rem;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(79, 70, 229, 0.1);
}

/* Deck Controls */
.deck-controls {
    margin-bottom: 25px;
    padding: 20px;
    background: var(--background-light);
    border-radius: var(--border-radius-small);
    border: 2px solid #e2e8f0;
}

.deck-selector {
    display: flex;
    align-items: center;
    gap: 15px;
    flex-wrap: wrap;
}

.deck-selector label {
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: 0;
    white-space: nowrap;
    min-width: 100px;
}

.deck-selector select {
    flex: 1;
    min-width: 200px;
    max-width: 300px;
    padding: 10px 12px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-small);
    font-size: 15px;
    background: white;
    transition: var(--transition);
}

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

.deck-selector button {
    margin: 0;
    padding: 10px 16px;
    font-size: 14px;
    background: var(--accent-color);
    white-space: nowrap;
}

.deck-selector button:hover {
    background: #059669;
}

.deck-selector button.delete-btn {
    background: var(--danger-color);
    margin-left: 8px;
}

.deck-selector button.delete-btn:hover:not(:disabled) {
    background: var(--danger-hover);
}

/* Study Mode Controls */
.study-mode-controls {
    text-align: center;
    margin-bottom: 25px;
}

.study-mode-controls button {
    background: var(--accent-color);
    margin: 5px 10px;
}

.study-mode-controls button:hover {
    background: #059669;
    box-shadow: 0 8px 24px rgba(16, 185, 129, 0.15);
}

/* Form styling with improved spacing */
.form-group {
    margin-bottom: 24px;
}

.form-group.form-row {
    display: flex;
    gap: 20px;
}

.form-group.form-row > div {
    flex: 1;
}

label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--text-color);
    font-size: 0.95rem;
}

input, textarea {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-small);
    font-size: 16px;
    font-family: inherit;
    transition: var(--transition);
    background: #ffffff;
}

input:focus, textarea:focus {
    outline: none;
    border-color: var(--border-color-focus);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
    transform: translateY(-2px);
}

textarea {
    resize: vertical;
    min-height: 90px;
    font-family: inherit;
}

/* Enhanced button styling */
button {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 14px 24px;
    border-radius: var(--border-radius-small);
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    font-family: inherit;
    transition: var(--transition);
    margin: 6px;
    position: relative;
    overflow: hidden;
}

button:hover:not(:disabled) {
    background: var(--primary-hover);
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
}

button:active:not(:disabled) {
    transform: translateY(-1px);
}

button:disabled {
    background: #9ca3af;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

button.delete-btn {
    background: var(--danger-color);
}

button.delete-btn:hover:not(:disabled) {
    background: var(--danger-hover);
    box-shadow: 0 8px 24px rgba(220, 38, 38, 0.15);
}

/* Card display area with improved layout */
.card-display {
    margin-top: 35px;
    padding: 25px;
    background: var(--background-light);
    border-radius: var(--border-radius);
    border: 2px solid #e2e8f0;
}

.card {
    background: var(--background-card);
    padding: 35px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    margin-bottom: 25px;
    min-height: 220px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
}

.card:hover {
    transform: translateY(-4px) scale(1.02);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary-color);
}

.card-content {
    font-size: 1.3rem;
    font-weight: 500;
    line-height: 1.5;
    color: var(--text-color);
}

.card-info {
    text-align: center;
    margin-bottom: 25px;
    font-size: 15px;
    color: var(--text-muted);
    font-weight: 500;
}

#study-progress {
    display: block;
    margin-top: 5px;
    font-weight: 600;
    color: var(--accent-color);
}

/* Study mode specific styles */
.study-mode #add-card-form {
    display: none;
}

.study-mode .deck-controls {
    display: none;
}

.study-mode .container {
    max-width: 700px; /* Slightly wider for study mode */
}

.study-mode .card {
    min-height: 250px;
    font-size: 1.1rem;
}

/* Utility classes */
.hidden {
    display: none !important;
}

/* Enhanced controls layout with better flexbox */
.controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 12px;
}

.controls button {
    flex: 1;
    min-width: 110px;
}

/* Enhanced responsive design */
@media (max-width: 900px) {
    .container {
        max-width: 650px;
        padding: 30px;
    }
    
    .deck-selector {
        flex-direction: column;
        align-items: stretch;
        gap: 12px;
    }
    
    .deck-selector label {
        margin-bottom: 8px;
        min-width: auto;
    }
    
    .deck-selector select {
        min-width: auto;
        max-width: none;
    }
}

@media (max-width: 650px) {
    .container {
        padding: 25px;
        margin: 10px;
        max-width: none;
    }
    
    h1 {
        font-size: 1.9rem;
        margin-bottom: 25px;
    }
    
    .controls {
        flex-direction: column;
    }
    
    .controls button {
        width: 100%;
        margin: 4px 0;
    }
    
    .card {
        padding: 25px;
        min-height: 180px;
    }
    
    .card-content {
        font-size: 1.1rem;
    }
    
    .study-mode-controls {
        margin-bottom: 20px;
    }
    
    .study-mode-controls button {
        display: block;
        width: 100%;
        margin: 5px 0;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 20px;
    }
    
    .card-display, .deck-controls {
        padding: 15px;
    }
    
    h1 {
        font-size: 1.7rem;
    }
    
    .card {
        padding: 20px;
        min-height: 160px;
    }
    
    button {
        padding: 12px 16px;
        font-size: 15px;
    }
}

.no-cards {
    text-align: center;
    color: var(--text-muted);
    font-style: italic;
    padding: 50px 20px;
    font-size: 1.1rem;
}

/* Add subtle animation for better UX */
.card-display, .form-group, .deck-controls {
    animation: fadeInUp 0.5s ease-out;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Smooth transitions for mode switching */
.study-mode-controls, .deck-controls {
    transition: opacity 0.3s ease, transform 0.3s ease;
}

.study-mode .deck-controls {
    opacity: 0;
    transform: translateY(-10px);
}

/* Accessibility improvements */
button:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

select:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

/* Keyboard shortcut hint styling */
.keyboard-hints {
    position: fixed;
    top: 20px;
    right: 20px;
    background: rgba(102, 126, 234, 0.95);
    color: white;
    padding: 12px 18px;
    border-radius: var(--border-radius);
    font-size: 13px;
    font-weight: 500;
    opacity: 0;
    transition: opacity 0.3s ease;
    pointer-events: none;
    z-index: 1000;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.keyboard-hints.show {
    opacity: 1;
}