  This paper presents my solution to the challenge "Riiid! Answer Correctness
Prediction" on Kaggle hosted by Riiid Labs (2020), which scores 0.817 (AUC) and
ranks 4th on the final private leaderboard. It is a single transformer-based
model heavily inspired from previous works such as SAKT, SAINT and SAINT+.
Novel ingredients that I believed to have made a difference are the time-aware
attention mechanism, the concatenation of the embeddings of the input sequences
and the embedding of continuous features.
