/* Style Apple inspiré */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            -webkit-font-smoothing: antialiased;
            -moz-osx-font-smoothing: grayscale;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Arial, sans-serif;
            background-color: #f5f5f7;
            color: #1d1d1f;
            line-height: 1.47059;
            font-weight: 400;
            letter-spacing: -0.022em;
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
        }

        .signup-container {
            width: 100%;
            max-width: 420px;
            background: #ffffff;
            border-radius: 18px;
            box-shadow: 0 4px 24px rgba(0, 0, 0, 0.06);
            overflow: hidden;
        }

        /* En-tête - Style Apple */
        .header {
            padding: 28px 28px 20px;
            text-align: center;
            border-bottom: 1px solid #d2d2d7;
        }

        .header h1 {
            font-size: 28px;
            font-weight: 600;
            color: #1d1d1f;
            margin-bottom: 4px;
        }

        .header p {
            font-size: 14px;
            color: #86868b;
            font-weight: 400;
        }

        /* Indicateur d'étape */
        .step-indicator {
            display: flex;
            justify-content: center;
            padding: 20px 28px 10px;
            gap: 8px;
        }

        .step-dot {
            width: 6px;
            height: 6px;
            border-radius: 50%;
            background-color: #d2d2d7;
            transition: all 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
        }

        .step-dot.active {
            width: 24px;
            border-radius: 3px;
            background-color: #007aff;
        }

        /* Conteneur du formulaire */
        .form-container {
            padding: 0 28px 28px;
        }

        .form-step {
            display: none;
            animation: fadeIn 0.3s ease-out;
        }

        .form-step.active {
            display: block;
        }

        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(8px); }
            to { opacity: 1; transform: translateY(0); }
        }

        .step-title {
            font-size: 20px;
            font-weight: 600;
            color: #1d1d1f;
            margin-bottom: 16px;
        }

        .step-description {
            font-size: 14px;
            color: #86868b;
            margin-bottom: 24px;
            line-height: 1.42859;
        }

        /* Champs de saisie */
        .input-group {
            margin-bottom: 20px;
        }

        .input-label {
            display: block;
            font-size: 13px;
            font-weight: 500;
            color: #424245;
            margin-bottom: 6px;
            letter-spacing: -0.01em;
        }

        .input-field {
            width: 100%;
            height: 44px;
            padding: 0 16px;
            font-size: 16px;
            font-family: inherit;
            background-color: #f5f5f7;
            border: 1px solid #d2d2d7;
            border-radius: 12px;
            color: #1d1d1f;
            transition: all 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
            -webkit-appearance: none;
        }

        .input-field:focus {
            outline: none;
            border-color: #007aff;
            background-color: #ffffff;
            box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.1);
        }

        .input-field.error {
            border-color: #ff3b30;
        }

        .input-field.success {
            border-color: #34c759;
        }

        .validation-message {
            font-size: 12px;
            margin-top: 6px;
            display: flex;
            align-items: center;
            gap: 4px;
            opacity: 0;
            transform: translateY(-4px);
            transition: all 0.3s ease;
        }

        .validation-message.show {
            opacity: 1;
            transform: translateY(0);
        }

        .validation-message.error {
            color: #ff3b30;
        }

        .validation-message.success {
            color: #34c759;
        }

        /* Règles de mot de passe */
        .password-rules {
            background-color: #f5f5f7;
            border-radius: 12px;
            padding: 16px;
            margin-top: 20px;
        }

        .password-rules-title {
            font-size: 14px;
            font-weight: 500;
            color: #1d1d1f;
            margin-bottom: 12px;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .rule-item {
            display: flex;
            align-items: center;
            gap: 8px;
            margin-bottom: 8px;
            font-size: 13px;
            color: #86868b;
            transition: color 0.3s ease;
        }

        .rule-item.valid {
            color: #34c759;
        }

        .rule-item i {
            font-size: 12px;
            width: 16px;
        }

        /* Conteneur des matières */
        .subjects-container {
            display: flex;
            flex-direction: column;
            gap: 16px;
            margin-top: 20px;
        }

        .subject-item {
            background-color: #f5f5f7;
            border-radius: 12px;
            padding: 16px;
            border: 1px solid transparent;
            transition: all 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
        }

        .subject-item:hover {
            background-color: #e8e8ed;
        }

        .subject-item:focus-within {
            border-color: #007aff;
            background-color: #ffffff;
        }

        .subject-header {
            display: flex;
            align-items: center;
            margin-bottom: 12px;
        }

        .subject-icon {
            width: 32px;
            height: 32px;
            border-radius: 8px;
            background-color: #007aff;
            display: flex;
            align-items: center;
            justify-content: center;
            margin-right: 12px;
        }

        .subject-icon i {
            color: #ffffff;
            font-size: 16px;
        }

        .subject-name {
            font-size: 16px;
            font-weight: 500;
            color: #1d1d1f;
        }

        .grade-input-container {
            display: flex;
            align-items: center;
            gap: 12px;
        }

        .grade-input {
            flex: 1;
            height: 44px;
            padding: 0 16px;
            font-size: 16px;
            font-family: inherit;
            background-color: #ffffff;
            border: 1px solid #d2d2d7;
            border-radius: 10px;
            text-align: center;
            color: #1d1d1f;
            transition: all 0.2s ease;
        }

        .grade-input:focus {
            outline: none;
            border-color: #007aff;
            box-shadow: 0 0 0 2px rgba(0, 122, 255, 0.1);
        }

        .grade-range {
            font-size: 13px;
            color: #86868b;
            min-width: 80px;
        }

        /* Options de paiement */
        .payment-option {
            background-color: #f5f5f7;
            border-radius: 12px;
            padding: 16px;
            border: 1px solid transparent;
            transition: all 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
            cursor: pointer;
        }

        .payment-option:hover {
            background-color: #e8e8ed;
        }

        .payment-option.selected {
            border-color: #007aff;
            background-color: #e8f3ff;
        }

        /* Avis important */
        .important-notice {
            background-color: #fff8e6;
            border-left: 4px solid #ff9500;
            border-radius: 0 8px 8px 0;
            padding: 16px;
            margin-top: 20px;
        }

        .important-notice-header {
            display: flex;
            align-items: center;
            margin-bottom: 8px;
        }

        .important-notice-header i {
            color: #ff9500;
            margin-right: 8px;
        }

        .important-notice-title {
            font-size: 14px;
            font-weight: 500;
            color: #1d1d1f;
        }

        .important-notice-text {
            font-size: 13px;
            color: #424245;
            line-height: 1.42859;
        }

        /* Boutons - Style Apple */
        .buttons-container {
            display: flex;
            justify-content: space-between;
            margin-top: 32px;
            padding-top: 20px;
            border-top: 1px solid #d2d2d7;
        }

        .apple-button {
            height: 44px;
            padding: 0 20px;
            font-size: 15px;
            font-weight: 500;
            font-family: inherit;
            border-radius: 10px;
            border: none;
            cursor: pointer;
            transition: all 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 8px;
            letter-spacing: -0.01em;
            -webkit-tap-highlight-color: transparent;
        }

        .apple-button:active {
            transform: scale(0.98);
        }

        .apple-button-primary {
            background-color: #007aff;
            color: #ffffff;
        }

        .apple-button-primary:hover:not(:disabled) {
            background-color: #0056cc;
        }

        .apple-button-secondary {
            background-color: transparent;
            color: #007aff;
            border: 1px solid #d2d2d7;
        }

        .apple-button-secondary:hover:not(:disabled) {
            background-color: #f5f5f7;
        }

        .apple-button:disabled {
            opacity: 0.4;
            cursor: not-allowed;
            transform: none;
        }

        /* Modal de confirmation */
        .modal-overlay {
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background-color: rgba(0, 0, 0, 0.4);
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
            z-index: 1000;
            opacity: 0;
            visibility: hidden;
            transition: all 0.3s ease;
        }

        .modal-overlay.active {
            opacity: 1;
            visibility: visible;
        }

        .modal-container {
            background-color: #ffffff;
            border-radius: 18px;
            width: 100%;
            max-width: 380px;
            padding: 28px;
            box-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
            transform: scale(0.9);
            transition: transform 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
        }

        .modal-overlay.active .modal-container {
            transform: scale(1);
        }

        .modal-header {
            text-align: center;
            margin-bottom: 20px;
        }

        .modal-icon {
            width: 60px;
            height: 60px;
            border-radius: 50%;
            background-color: #34c759;
            display: flex;
            align-items: center;
            justify-content: center;
            margin: 0 auto 16px;
        }

        .modal-icon i {
            color: #ffffff;
            font-size: 24px;
        }

        .modal-title {
            font-size: 22px;
            font-weight: 600;
            color: #1d1d1f;
            margin-bottom: 8px;
        }

        .modal-message {
            font-size: 15px;
            color: #424245;
            line-height: 1.47059;
            text-align: center;
            margin-bottom: 24px;
        }

        .modal-message strong {
            color: #1d1d1f;
        }

        .modal-button {
            width: 100%;
            height: 44px;
            background-color: #007aff;
            color: #ffffff;
            border: none;
            border-radius: 10px;
            font-size: 15px;
            font-weight: 500;
            font-family: inherit;
            cursor: pointer;
            transition: all 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
        }

        .modal-button:hover {
            background-color: #0056cc;
        }

        /* Indicateur de chargement */
        .loading-spinner {
            display: none;
            text-align: center;
            margin: 20px 0;
        }

        .loading-spinner.active {
            display: block;
        }

        .spinner {
            width: 40px;
            height: 40px;
            border: 3px solid #f3f3f3;
            border-top: 3px solid #007aff;
            border-radius: 50%;
            animation: spin 1s linear infinite;
            margin: 0 auto;
        }

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

        /* Message d'erreur */
        .error-message-container {
            background-color: #ffeaea;
            border: 1px solid #ffcdd2;
            border-radius: 10px;
            padding: 15px;
            margin: 20px 0;
            text-align: center;
        }

        .error-message-container i {
            color: #ff3b30;
            font-size: 24px;
            margin-bottom: 10px;
        }

        .error-message-container h3 {
            color: #ff3b30;
            margin-bottom: 8px;
        }

        .error-message-container p {
            color: #666;
            margin-bottom: 15px;
        }

        /* Design responsive */
        @media (max-width: 480px) {
            body {
                padding: 12px;
                align-items: flex-start;
                padding-top: 20px;
            }

            .signup-container {
                border-radius: 14px;
            }

            .header {
                padding: 20px 20px 16px;
            }

            .header h1 {
                font-size: 24px;
            }

            .form-container {
                padding: 0 20px 20px;
            }

            .subject-item, .payment-option {
                padding: 14px;
            }

            .grade-input-container {
                flex-direction: column;
                align-items: stretch;
                gap: 8px;
            }

            .grade-range {
                text-align: center;
            }

            .buttons-container {
                flex-direction: column;
                gap: 12px;
            }

            .apple-button {
                width: 100%;
            }

            .modal-container {
                padding: 24px;
            }
        }

        /* États focus pour l'accessibilité */
        .apple-button:focus-visible,
        .input-field:focus-visible,
        .grade-input:focus-visible {
            outline: 2px solid #007aff;
            outline-offset: 2px;
        }