:root {
    --bg-color: #0f172a;
    --panel-bg: #1e293b;
    --text-color: #f8fafc;
    --accent-primary: #3b82f6;
    --accent-hover: #2563eb;
    --accent-danger: #ef4444;
    --border-color: #334155;
    --font-family: 'Outfit', sans-serif;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    overflow: hidden;
}

.app-container {
    display: flex;
    flex-direction: column;
    width: 100%;
    height: 100%;
}

.controls-panel {
    background-color: var(--panel-bg);
    padding: 20px 40px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

h1 {
    font-size: 1.5rem;
    font-weight: 800;
}

h1 span {
    color: var(--accent-primary);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

label {
    font-size: 0.9rem;
    font-weight: 600;
    color: #cbd5e1;
}

select, input[type="range"] {
    background: #0f172a;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    padding: 8px 12px;
    border-radius: 6px;
    font-family: var(--font-family);
    font-size: 1rem;
    outline: none;
    transition: border-color 0.2s;
}

select:focus {
    border-color: var(--accent-primary);
}

.action-buttons {
    flex-direction: row;
    align-items: flex-end;
    gap: 12px;
}

.btn {
    padding: 10px 24px;
    border: none;
    border-radius: 8px;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    font-family: var(--font-family);
    transition: transform 0.1s, background-color 0.2s, opacity 0.2s;
}

.btn:active {
    transform: scale(0.95);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

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

.btn.primary:hover:not(:disabled) {
    background-color: var(--accent-hover);
}

.btn.secondary {
    background-color: transparent;
    border: 1px solid var(--accent-danger);
    color: var(--accent-danger);
}

.btn.secondary:hover:not(:disabled) {
    background-color: rgba(239, 68, 68, 0.1);
}

.flashcard-area {
    flex-grow: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    padding: 20px;
    min-height: 0;
}

.status-message {
    font-size: 1.5rem;
    color: #64748b;
    font-weight: 600;
}

.flashcard {
    width: 100%;
    height: 100%;
    max-width: 1600px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background-color: var(--panel-bg);
    border-radius: 32px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    padding: 40px;
}

.flashcard.hidden {
    display: none;
}

#card-image {
    max-width: 100%;
    max-height: 60vh;
    object-fit: contain;
    border-radius: 12px;
}

.card-word {
    margin-top: 20px;
    font-size: 8vw;
    font-weight: 800;
    text-transform: capitalize;
    color: var(--text-color);
    letter-spacing: 2px;
    text-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

/* Responsive Design for Mobile and Tablets */
@media (max-width: 768px) {
    .flashcard-area {
        padding: 10px; /* Maximize screen usage */
    }

    .controls-panel {
        flex-direction: column;
        align-items: stretch;
        gap: 15px;
        padding: 15px 20px;
        overflow-y: auto;
        max-height: 45vh; /* Ensure controls don't consume the whole screen */
    }

    .controls-panel h1 {
        text-align: center;
        margin-bottom: 5px;
    }

    .control-group {
        flex-direction: row;
        align-items: center;
        justify-content: space-between;
        gap: 15px;
    }
    
    .control-group[style*="margin-top"] {
        margin-top: 0 !important;
    }
    
    select, input[type="range"] {
        flex: 1;
        max-width: 60%;
    }

    .action-buttons {
        justify-content: space-between;
        margin-top: 5px;
    }

    .btn {
        flex: 1;
        padding: 12px 10px;
    }
    
    .flashcard {
        padding: 10px;
        border-radius: 16px;
    }

    #card-image {
        flex-grow: 1;
        width: 100%;
        height: 0; /* Important for flex-grow to work properly with images */
        max-height: none;
    }

    .card-word {
        font-size: 18vw; /* Make text bigger relative to narrow screen */
        margin-top: 10px;
    }
}