Learn Spanish (Latin America): No quisiste lijar el piso, de modo que el azulejo se quedó sucio. - You didn't want to sand the floor, so the tile ended up dirty.

De modo que can introduce either a result (meaning 'so' or 'as a result') or a purpose (meaning 'in order to'). Because the dirty tile is an actual, completed result of not sanding the floor, we use the indicative (se quedó). If the speaker were expressing an intended purpose, like doing something specifically so that the tile would stay dirty, they would use the subjunctive (se quedara).

Why use the preterite no quisiste instead of the imperfect no querías for 'didn't want'?

In the preterite, no querer implies a direct refusal or a completed decision at a specific moment in the past, basically meaning 'you refused'. Using the imperfect (no querías) would simply describe an ongoing background state of mind, like 'you didn't feel like it', without necessarily pointing to a specific moment of refusal.

Why use se quedó instead of estaba or estuvo to say it 'ended up' dirty?

The reflexive verb quedarse is frequently used to mean 'to end up' or 'to remain' in a specific state after an event or action. While estaba sucio just describes the state ('it was dirty'), se quedó sucio emphasizes the final resulting condition caused by skipping the sanding.

Could I use de tal modo que instead of de modo que in this sentence?