@font-face {
  font-family: 'KaTeX_Main_Minus';
  src: url('https://cdn.jsdelivr.net/npm/katex@0.16.8/dist/fonts/KaTeX_Main-Regular.woff2') format('woff2'),
       url('https://cdn.jsdelivr.net/npm/katex@0.16.8/dist/fonts/KaTeX_Main-Regular.woff') format('woff'),
       url('https://cdn.jsdelivr.net/npm/katex@0.16.8/dist/fonts/KaTeX_Main-Regular.ttf') format('truetype');
  font-weight: 100 900;
  font-style: normal;
  unicode-range: U+2212;
}

:root {
    --primary-color: #0284c7;
    --primary-hover: #0369a1;
    --success-color: #10B981;
    --error-color: #EF4444;
    --text-main: #1F2937;
    --text-muted: #6B7280;
    --bg-card: rgba(255, 255, 255, 0.95);
    --border-card: rgba(255, 255, 255, 0.6);
}

.exercise-wrapper {
    font-family: 'Inter', sans-serif;
    color: var(--text-main);
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    border-radius: 12px;
    padding: 15px 20px;
    overflow: hidden;
}

.app-container {
    width: 100%;
    max-width: 700px;
    padding: 0px 10px 10px 10px;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.app-header {
    text-align: center;
}

.glass-card {
    background: var(--bg-card);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-card);
    border-radius: 20px;
    padding: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05), inset 0 1px 0 rgba(255, 255, 255, 0.6);
    display: flex;
    flex-direction: column;
    gap: 18px;
}

.exercise-section {
    background: white;
    padding: 16px;
    border-radius: 12px;
    text-align: center;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.02);
    border: 1px solid #E5E7EB;
}

.context-box {
    background: #F0FDF4;
    border: 1px solid #86EFAC;
    border-radius: 8px;
    padding: 8px 12px;
    margin-bottom: 12px;
    display: inline-block;
    color: #166534;
    font-weight: 600;
    font-size: 1.05rem;
}

.figure-box {
    margin: 8px auto 12px auto;
    max-width: 340px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.expression-box {
    background: #F8FAFC;
    border: 2px solid #E2E8F0;
    border-radius: 12px;
    padding: 14px 18px;
    margin: 8px auto 14px auto;
    display: inline-block;
    max-width: 100%;
    box-shadow: 0 2px 6px rgba(0,0,0,0.03);
}

.expression-text {
    font-size: 1.45rem;
    font-weight: 700;
    color: #0F172A;
}

/* Zone d'entrée de réponse avec prévisualisation vectorielle */
.input-section {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
}

.vector-answer-display {
    min-width: 160px;
    min-height: 54px;
    padding: 6px 16px;
    background: #FFFFFF;
    border: 2.5px solid #CBD5E1;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.6rem;
    font-weight: bold;
    color: #0284C7;
    cursor: text;
    transition: all 0.2s ease;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.04);
}

.vector-answer-display.active-input {
    border-color: #0284C7;
    box-shadow: 0 0 0 3px rgba(2, 132, 199, 0.25);
    background: #F0F9FF;
}

.vector-placeholder {
    color: #94A3B8;
    font-size: 1.1rem;
    font-style: italic;
    font-weight: normal;
}

/* Clavier virtuel pour le calcul vectoriel */
.virtual-keyboard {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
    max-width: 480px;
    margin: 0 auto;
}

.vk-btn {
    min-width: 50px;
    height: 48px;
    padding: 6px 12px;
    background: #ffffff;
    border: 1.5px solid #d1d5db;
    border-radius: 10px;
    font-size: 1.25rem;
    font-weight: 700;
    color: #1f2937;
    cursor: pointer;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    transition: all 0.15s ease;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
}

.vk-btn:hover:not(:disabled) {
    background: #f3f4f6;
    border-color: #9ca3af;
    transform: translateY(-1px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.08);
}

.vk-btn:active:not(:disabled) {
    transform: translateY(1px);
    box-shadow: 0 1px 2px rgba(0,0,0,0.05);
}

.vk-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.vk-zero {
    background: #FEF3C7;
    border-color: #F59E0B;
    color: #B45309;
    font-size: 1.3rem;
    min-width: 64px;
}

.vk-zero:hover:not(:disabled) {
    background: #FDE68A;
    border-color: #D97706;
}

.vk-del {
    background: #FEE2E2;
    border-color: #F87171;
    color: #DC2626;
    font-size: 1.2rem;
    min-width: 60px;
}

.vk-del:hover:not(:disabled) {
    background: #FECACA;
}

.vk-clear {
    background: #F3F4F6;
    border-color: #9CA3AF;
    color: #4B5563;
    font-size: 0.95rem;
}

/* Feedback */
.feedback {
    padding: 12px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    font-weight: 600;
    font-size: 1.05rem;
    animation: fadeIn 0.3s ease-out;
}

.feedback.success {
    background-color: #D1FAE5;
    color: #065F46;
    border: 1px solid #A7F3D0;
}

.feedback.error {
    background-color: #FEE2E2;
    color: #991B1B;
    border: 1px solid #FECACA;
}

.feedback.warning {
    background-color: #FEF3C7;
    color: #92400E;
    border: 1px solid #FDE68A;
}

/* Boutons principaux */
.btn {
    border: none;
    border-radius: 10px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.primary-btn {
    background: linear-gradient(135deg, #059669 0%, #10B981 100%);
    color: white;
}

.primary-btn:hover {
    background: linear-gradient(135deg, #047857 0%, #059669 100%);
    box-shadow: 0 6px 12px -2px rgba(16, 185, 129, 0.3);
}

.blue-btn {
    background: linear-gradient(135deg, #0284c7 0%, #0369a1 100%);
    color: white;
    padding: 10px 24px;
}

.blue-btn:hover {
    background: linear-gradient(135deg, #0369a1 0%, #075985 100%);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(-5px); }
    to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 640px) {
    .glass-card {
        padding: 14px;
        gap: 12px;
    }
    .expression-text {
        font-size: 1.2rem;
    }
    .vk-btn {
        min-width: 44px;
        height: 44px;
        font-size: 1.15rem;
        padding: 4px 8px;
    }
}