:root {
    /* TODO: Définissez votre palette de couleurs ici */
    --bg-color: #f0f2f5;
    --btn-bg: #e0e0e0;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: sans-serif;
}

/* --- STYLE GÉNÉRAL --- */
body {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    color: var(--text-color);
}

.app-container {
    background: white;
    padding: 2rem;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    width: 100%;
    max-width: 450px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #eee;
    padding-bottom: 1rem;
}

h1 {
    font-size: 1.5rem;
    font-weight: 600;
}

.back-btn {
    text-decoration: none;
    color: #777;
    font-weight: 500;
    transition: color 0.3s;
}

.back-btn:hover {
    color: #333;
}

/* --- ZONE CALCULATRICE (À PERSONNALISER) --- */
.calculatrice {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 10px;
}

.ecran {
    grid-column: 1 / -1;
    background-color: #222;
    color: white;
    min-height: 100px;
    padding: 20px;
    border-radius: 10px;
    text-align: right;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
}

.operande-precedent {
    /* TODO */
}

.operande-actuel {
    /* TODO */
}

button {
    cursor: pointer;
    border: none;
    padding: 15px;
    font-size: 1.25rem;
    border-radius: 10px;
}

/* ... Ajoutez votre style pour les boutons ici ... */

button:hover {
    /* TODO: Effet de survol */
}

button.etendre-deux {
    grid-column: span 2;
}

/* --- SECTION TÂCHES (NE PAS MODIFIER SI POSSIBLE) --- */
.section-taches {
    margin-top: 1rem;
    border-top: 1px solid #eee;
    padding-top: 1rem;
}

.section-taches h2 {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
    color: #777;
}

#conteneur-taches {
    font-size: 0.9rem;
    background: #f9f9f9;
    padding: 1rem;
    border-radius: 10px;
    max-height: 200px;
    overflow-y: auto;
}

#conteneur-taches ul {
    list-style-type: none;
    padding-left: 0;
}

#conteneur-taches li {
    margin-bottom: 5px;
    padding-left: 20px;
    position: relative;
}

#conteneur-taches li::before {
    content: '○';
    position: absolute;
    left: 0;
    color: #ff9f43;
    font-size: 0.8rem;
    top: 2px;
}

.tache-faite {
    text-decoration: line-through;
    color: #aaa;
}