* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

:root {
    --green-primary: #10b981;
    --green-dark: #047857;
    --green-light: #d1fae5;
    --green-extra-light: #ecfdf5;
    --gradient-green: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --gradient-green-light: linear-gradient(135deg, #34d399 0%, #10b981 100%);
    --shadow-light: 0 8px 32px rgba(16, 185, 129, 0.15);
    --shadow-hover: 0 20px 40px rgba(16, 185, 129, 0.3);
    --shadow-neumorph: 8px 8px 16px rgba(16, 185, 129, 0.2), -8px -8px 16px rgba(255, 255, 255, 0.8);
    --border-light: 1px solid rgba(16, 185, 129, 0.2);
    --border-glow: 1px solid rgba(16, 185, 129, 0.5);
    --radius: 20px;
    --radius-sm: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    background: linear-gradient(135deg, #ecfdf5 0%, #d1fae5 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
    position: relative;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at 20% 80%, rgba(16, 185, 129, 0.1) 0%, transparent 50%),
                radial-gradient(circle at 80% 20%, rgba(16, 185, 129, 0.05) 0%, transparent 50%);
    z-index: -1;
}

.container {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(20px);
    padding: 40px 30px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-light), inset 0 1px 0 rgba(255, 255, 255, 0.8);
    width: 100%;
    max-width: 520px;
    text-align: center;
    position: relative;
    animation: fadeInUp 0.6s ease-out;
    border: var(--border-light);
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

h1 {
    background: var(--gradient-green);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-size: clamp(1.8rem, 4vw, 2.5rem);
    font-weight: 800;
    margin-bottom: 30px;
    letter-spacing: -0.02em;
    text-shadow: 0 2px 4px rgba(16, 185, 129, 0.3);
}

.control-group {
    margin-bottom: 24px;
    text-align: left;
    position: relative;
}

label {
    display: block;
    margin-bottom: 12px;
    font-weight: 600;
    color: var(--green-dark);
    font-size: 0.95rem;
    letter-spacing: 0.5px;
}

label::before {
    content: '✦ ';
    color: var(--green-primary);
    font-weight: bold;
}

select {
    appearance: none;
    width: 100%;
    padding: 16px 20px 16px 16px;
    background: rgba(255, 255, 255, 0.8);
    border: var(--border-light);
    border-radius: var(--radius-sm);
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
    backdrop-filter: blur(10px);
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.05);
}

select:focus {
    outline: none;
    border-color: var(--green-primary);
    box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.1);
}

select:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-light);
}

select::after {
    content: '▼';
    position: absolute;
    right: 16px;
    top: 50%;
    transform: translateY(-50%);
    pointer-events: none;
    color: var(--green-dark);
}

.btn-upload, .btn-download {
    display: block;
    width: 100%;
    padding: 18px 24px;
    background: var(--gradient-green);
    color: white;
    text-align: center;
    border-radius: var(--radius-sm);
    cursor: pointer;
    border: none;
    font-size: 1.1rem;
    font-weight: 700;
    transition: var(--transition);
    box-shadow: var(--shadow-light);
    position: relative;
    overflow: hidden;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.btn-upload::before, .btn-download::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3), transparent);
    transition: left 0.5s;
}

.btn-upload:hover::before, .btn-download:hover::before {
    left: 100%;
}

.btn-upload:hover, .btn-download:not(:disabled):hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
}

.btn-upload:active, .btn-download:not(:disabled):active {
    transform: translateY(-1px);
}

.btn-download:disabled {
    background: #9ca3af;
    cursor: not-allowed;
    transform: none;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.canvas-container {
    position: relative;
    width: 100%;
    aspect-ratio: 1;
    border-radius: var(--radius);
    overflow: hidden;
    margin-bottom: 20px;
    background: var(--green-extra-light);
    border: 2px solid rgba(16, 185, 129, 0.3);
    box-shadow: inset 0 4px 12px rgba(16, 185, 129, 0.1), var(--shadow-light);
    transition: var(--transition);
}

.canvas-container:hover {
    box-shadow: inset 0 4px 12px rgba(16, 185, 129, 0.15), var(--shadow-hover);
}

canvas {
    width: 100%;
    height: 100%;
    cursor: grab;
    border-radius: var(--radius);
    display: block;
}

canvas:active {
    cursor: grabbing;
}

.loading-spinner {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    color: var(--green-dark);
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s;
}

.loading-spinner.active {
    opacity: 1;
}

.spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--green-light);
    border-top: 4px solid var(--green-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.hint {
    font-size: 0.85rem;
    color: #6b7280;
    margin-top: 8px;
    text-align: center;
    font-style: italic;
    letter-spacing: 0.3px;
}

/* Custom Range Slider */
input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 8px;
    border-radius: 5px;
    background: rgba(16, 185, 129, 0.2);
    outline: none;
    margin: 12px 0;
    cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--gradient-green);
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
    transition: var(--transition);
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.1);
    box-shadow: 0 6px 16px rgba(16, 185, 129, 0.5);
}

input[type="range"]::-moz-range-thumb {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--gradient-green);
    cursor: pointer;
    border: none;
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
}

input[type="range"]::-moz-range-progress {
    background: var(--green-primary);
    height: 8px;
    border-radius: 5px;
}

/* Responsive */
@media (max-width: 480px) {
    .container {
        padding: 30px 20px;
        margin: 10px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    .canvas-container {
        border-radius: var(--radius-sm);
    }
}

/* Mobile Touch Optimizations */
@media (hover: none) and (pointer: coarse) {
    .btn-upload, .btn-download {
        padding: 20px;
        font-size: 1.2rem;
    }
    
    canvas {
        cursor: -webkit-grab;
        cursor: grab;
    }
}