diff --git a/grade_school_math/train.py b/grade_school_math/train.py
index 01f3450..3276913 100644
--- a/grade_school_math/train.py
+++ b/grade_school_math/train.py
@@ -1,50 +1,82 @@
 import torch as th
 from dataset import get_examples, GSMDataset
-from transformers import GPT2Tokenizer, GPT2LMHeadModel
-from transformers import GPT2Config, AdamW
-from transformers import get_scheduler
-from tqdm.auto import tqdm
+from transformers import (
+    GPT2Tokenizer, GPT2LMHeadModel, GPT2Config,
+    AdamW, get_scheduler
+)
 from torch.utils.data import DataLoader
+from tqdm.auto import tqdm
+
+# === CLASS 1: Tokenizer Loader ===
+class TokenizerLoader:
+    @staticmethod
+    def load(name="gpt2"):
+        return GPT2Tokenizer.from_pretrained(name)
+
+# === CLASS 2: Dataset + Dataloader ===
+class DataLoaderBuilder:
+    def __init__(self, tokenizer, batch_size=16):
+        examples = get_examples("train")
+        dataset = GSMDataset(tokenizer, examples)
+        self.loader = DataLoader(dataset, batch_size=batch_size, shuffle=True)
+
+    def get_loader(self):
+        return self.loader
 
+# === CLASS 3: Model + Optimizer ===
+class ModelBuilder:
+    def __init__(self, model_name="gpt2", lr=1e-5, total_steps=1000):
+        config = GPT2Config.from_pretrained(model_name)
+        self.model = GPT2LMHeadModel.from_pretrained(model_name, config=config)
+        self.device = th.device("cuda" if th.cuda.is_available() else "cpu")
+        self.model.to(self.device)
+        self.model.train()
+        self.optimizer = AdamW(self.model.parameters(), lr=lr)
+        self.scheduler = get_scheduler(
+            "linear", optimizer=self.optimizer,
+            num_warmup_steps=0, num_training_steps=total_steps
+        )
 
+# === CLASS 4: Trainer ===
+class Trainer:
+    def __init__(self, model, optimizer, scheduler, device):
+        self.model = model
+        self.optimizer = optimizer
+        self.scheduler = scheduler
+        self.device = device
+
+    def train(self, dataloader, num_epochs):
+        pbar = tqdm(range(num_epochs * len(dataloader)))
+        for epoch in range(num_epochs):
+            for batch in dataloader:
+                self.optimizer.zero_grad()
+                batch = {k: v.to(self.device) for k, v in batch.items()}
+                outputs = self.model(**batch, labels=batch["input_ids"])
+                loss = outputs[0]
+                loss.backward()
+                self.optimizer.step()
+                self.scheduler.step()
+                pbar.update(1)
+                pbar.set_description(f"train_loss: {loss.item():.5f}")
+
+# === MAIN FUNCTION ===
 def main():
-    tokenizer = GPT2Tokenizer.from_pretrained("gpt2")
-    train_examples = get_examples("train")
-    train_dset = GSMDataset(tokenizer, train_examples)
-
-    device = th.device("cuda")
-    config = GPT2Config.from_pretrained("gpt2")
-    model = GPT2LMHeadModel.from_pretrained("gpt2", config=config)
-    model.to(device)
-    model.train()
-
-    train_loader = DataLoader(train_dset, batch_size=16, shuffle=True)
-    optim = AdamW(model.parameters(), lr=1e-5)
-
-    num_epochs = 20
-    num_training_steps = num_epochs * len(train_loader)
-    lr_scheduler = get_scheduler(
-        "linear",
-        optimizer=optim,
-        num_warmup_steps=0,
-        num_training_steps=num_training_steps,
-    )
+    tokenizer = TokenizerLoader.load("gpt2")
+    data_builder = DataLoaderBuilder(tokenizer)
+    train_loader = data_builder.get_loader()
 
-    pbar = tqdm(range(num_training_steps))
-    for epoch in range(num_epochs):
-        for batch in train_loader:
-            optim.zero_grad()
-            batch = {k: v.to(device) for k, v in batch.items()}
-            outputs = model(**batch, labels=batch["input_ids"])
-            loss = outputs[0]
-            loss.backward()
-            optim.step()
-            lr_scheduler.step()
-            pbar.update(1)
-            pbar.set_description(f"train_loss: {loss.item():.5f}")
-
-    model.save_pretrained("model_ckpts/")
+    total_steps = len(train_loader) * 20
+    model_builder = ModelBuilder("gpt2", lr=1e-5, total_steps=total_steps)
+
+    trainer = Trainer(
+        model_builder.model,
+        model_builder.optimizer,
+        model_builder.scheduler,
+        model_builder.device
+    )
+    trainer.train(train_loader, num_epochs=20)
 
+    model_builder.model.save_pretrained("model_ckpts/")
 
 if __name__ == "__main__":
     main()