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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); /* default (medium) */
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    transition: background 0.5s ease;
}

/* background gradient variations for each difficulty */
body.bg-easy {
    background: linear-gradient(135deg, #a8e063 0%, #56ab2f 100%);
}

body.bg-medium {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

body.bg-hard {
    background: linear-gradient(135deg, #ff6b6b 0%, #ff8e53 100%);
}
.container {
    background: white;
    border-radius: 15px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
    padding: 40px;
    max-width: 600px;
    width: 100%;
    text-align: center;
}

h1 {
    color: #333;
    margin-bottom: 30px;
    font-size: 2.5em;
}

.control-panel {
    margin-bottom: 30px;
    display: flex;
    justify-content: center;
    gap: 15px;
    align-items: center;
}

label {
    font-weight: 600;
    color: #555;
    font-size: 1.1em;
}

select {
    padding: 10px 15px;
    /*border: 2px solid #667eea;*/
    border: hidden;
    border-radius: 8px;
    background: #f8f9fa;
    color: #333;
    font-size: 1em;
    cursor: pointer;
    transition: all 0.3s ease;
}

select:hover {
    border-color: #764ba2;
}

select:focus {
    outline: none;
    box-shadow: 0 0 10px rgba(102, 126, 234, 0.5);
}

.challenge-display {
    background: #f8f9fa;
    /*border-left: 5px solid #667eea;*/
    padding: 30px;
    border-radius: 8px;
    margin-bottom: 30px;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
}

#challenge-text {
    font-size: 1.5em;
    color: #333;
    line-height: 1.6;
    font-weight: 500;
}

.btn-generate {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); /* default medium */
    color: white;
    border: none;
    padding: 15px 40px;
    font-size: 1.1em;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 600;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.btn-easy {
    background: linear-gradient(135deg, #a8e063 0%, #f8ff00 100%); /* green + yellow */
}

.btn-medium {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); /* blue + purple */
}

.btn-hard {
    background: linear-gradient(135deg, #ff758c 0%, #ff7eb3 100%); /* pink + orange-ish */
}
.btn-generate:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

.btn-generate:active {
    transform: translateY(0);
}