:root {
    --primary-color: #059669;
    --primary-hover: #047857;
    --primary-light: #dcfce7;
    --secondary-color: #f1f5f9;
    --secondary-hover: #e2e8f0;
    --text-color: #1e293b;
    --text-muted: #64748b;
    --card-bg: rgba(255, 255, 255, 0.95);
    --border-color: #bbf7d0;
    --success-color: #10b981;
    --error-color: #ef4444;
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    color: var(--text-color);
    margin: 0;
    padding: 0;
}

.exercise-wrapper {
    position: relative;
    width: 100%;
    border-radius: 1.25rem;
    padding: 1.5rem;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.05), 0 8px 10px -6px rgba(0, 0, 0, 0.01);
    background: linear-gradient(135deg, #dcfce7 0%, #bbf7d0 100%);
    overflow: hidden;
    box-sizing: border-box;
}

.background-mesh {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(at 10% 20%, rgba(13, 148, 136, 0.12) 0px, transparent 50%),
        radial-gradient(at 90% 80%, rgba(20, 184, 166, 0.15) 0px, transparent 50%);
    pointer-events: none;
    z-index: 0;
}

.app-container {
    position: relative;
    z-index: 1;
    max-width: 600px;
    margin: 0 auto;
}

.app-header {
    text-align: center;
    margin-bottom: 1.25rem;
}

.card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    padding: 1.5rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
}

.exercise-section {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 80px;
    margin-bottom: 1.25rem;
    background: white;
    border-radius: 0.75rem;
    border: 2px dashed #5eead4;
    padding: 1rem;
}

.math-display {
    font-size: 1.5rem;
    font-weight: 600;
    color: #134e4a;
}

.input-section {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1.25rem;
}

.input-section input {
    flex: 1;
    font-size: 1.35rem;
    text-align: center;
    font-weight: 700;
    border: 2px solid #5eead4;
    border-radius: 0.75rem;
    padding: 0.6rem;
    outline: none;
    transition: all 0.2s;
    background: #ffffff;
    color: #134e4a;
}

.input-section input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 4px rgba(13, 148, 136, 0.15);
}

.btn {
    font-weight: 600;
    border-radius: 0.75rem;
    padding: 0.6rem 1.25rem;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
}

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

.primary-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

.secondary-btn {
    background: var(--secondary-color);
    color: var(--text-color);
}

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

.virtual-keyboard {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 0.4rem;
    margin-bottom: 1.25rem;
}

.vk-btn {
    font-size: 1.2rem;
    font-weight: bold;
    padding: 0.6rem 0.2rem;
    background: white;
    border: 1px solid #99f6e4;
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.15s;
    color: #134e4a;
    box-shadow: 0 2px 4px rgba(0,0,0,0.03);
}

.vk-btn:hover {
    background: #f0fdfa;
    border-color: var(--primary-color);
    transform: translateY(-1px);
}

.vk-btn:active {
    transform: translateY(1px);
}

.vk-clear, .vk-backspace, .vk-del, .vk-comma {
    font-weight: 700;
}

.vk-clear {
    background: #fee2e2;
    color: #991b1b;
    border-color: #fca5a5;
}

.vk-clear:hover {
    background: #fecaca;
}

.vk-backspace, .vk-del {
    background: #ffedd5;
    color: #9a3412;
    border-color: #fdba74;
}

.vk-backspace:hover, .vk-del:hover {
    background: #fed7aa;
}

.vk-comma {
    background: #e0e7ff;
    color: #3730a3;
    border-color: #a5b4fc;
    font-size: 1.4rem;
}

.feedback-message {
    padding: 0.75rem;
    border-radius: 0.5rem;
    font-weight: 600;
    text-align: center;
    margin-bottom: 1rem;
    display: none;
}

.feedback-success {
    display: block;
    background-color: #d1fae5;
    color: #065f46;
    border: 1px solid #6ee7b7;
}

.feedback-error {
    display: block;
    background-color: #fee2e2;
    color: #991b1b;
    border: 1px solid #fca5a5;
}

.feedback-info {
    display: block;
    background-color: #e0f2fe;
    color: #0369a1;
    border: 1px solid #7dd3fc;
}

.actions-section {
    display: flex;
    justify-content: center;
}