## 3 Results and Discussion
### WCAG Compliance Analysis

Table 2: Results of the WCAG analysis—errors and alerts. sum of the four preceding cells in each row. The rows marked from 1 to 25 are devoted to particular problem categories. The last row of the table is called \"number of distinct problem categories\", and it holds the number of non-zero cells within the columns holding numbers of problems. Descriptions of the problem categories, and the threats they pose to accessibility, can be found within the WAVE tool documentation [50]. Scratch seems to be the least problematic environment in terms of accessibility. Nine distinct categories of problems were observed: linked image missing alternative text, missing alternative text, missing form label, very low contrast, image with title, no heading structure, noscript element, orphaned form label, and very small text. The biggest number of problem occurrences was observed in the categories missing alternative text and very small text, that belong to the WCAG perceivable area. Occurrences in the remaining categories were incidental. In the case of App Inventor, problems were detected in 15 different categories. The biggest number of problem occurrences (significantly exceeding the results for Scratch) was registered for the WCAG perceivable area within the categories: missing alternative text, missing form label, spacer image missing alternative text, layout table, and empty form label. What is new is that the assessment revealed problems in the WCAG operable area (especially the redundant link category) and the understandable area (language missing or invalid, and missing labels). Occurrences in the remaining categories were incidental. Despite these results, it has to be concluded that App Inventor is a quite successful environment, with millions of users that have created millions of applications. The numbers presented may suggest that it is implemented using a style or technology that is more prone to accessibility errors than in the case of Scratch. In the case of StarLogo, problems were detected in 18 distinct categories, which is the highest score among the tested environments. The biggest number of problem occurrences was noted in the WCAG perceivable area within the categories missing form label, very low contrast, and select missing label. Occurrences in the remaining categories were incidental, although categories of problems from the WCAG operable area are broadly affected. In general, the main problems of all environments are missing or improper labels/ alternative texts, a distorted page structure, redundant links, and problems with a low contrast of graphical interface elements. What are the expected outcomes? If an alternative text/label, e.g., in the case of images, buttons, and links is missing, screen readers for blind users are not able to describe them properly, the purpose of an interface element. Missing headings and headings with no content make navigation problematic for the user, e.g., skipping empty headings when using a keyboard to navigate might be tiresome for the user. Low contrast and very small text deteriorate interface accessibility for visually impaired users. Contrast problems basically only concerned StarLogo and visual symbols within the palette and work area. Redundant links mean that many links on the same webpage direct to the same resource or interface section. This can cause redundant navigation when using screen readers or keyboard navigation. An interesting case is the presence of noscript content, which is available only if JavaScript is disabled. Because the vast majority of users, including those using assistive technologies, are script-enabled, noscript elements cannot be used to deliver content. Finally, a tabular layout detected in the case of App Inventor might introduce order and navigation issues.