diff --git a/src/obpf/include/obpf/simulator.h b/src/obpf/include/obpf/simulator.h
index 4d511e2..6fbb57f 100644
--- a/src/obpf/include/obpf/simulator.h
+++ b/src/obpf/include/obpf/simulator.h
@@ -16,10 +16,7 @@ extern "C" {
 
     typedef struct {
         uint8_t count;
-        uint8_t first;
-        uint8_t second;
-        uint8_t third;
-        uint8_t fourth;
+        uint8_t lines[4];
         uint64_t countdown;
         uint64_t delay;
     } ObpfLineClearDelayState;
@@ -65,12 +62,12 @@ extern "C" {
     OBPF_EXPORT uint64_t obpf_tetrion_get_next_frame(struct ObpfTetrion const* tetrion);
     OBPF_EXPORT void obpf_tetrion_simulate_next_frame(struct ObpfTetrion* tetrion, ObpfKeyState key_state);
     OBPF_EXPORT void obpf_destroy_tetrion(struct ObpfTetrion const* tetrion);
-    OBPF_EXPORT struct ObpfMatrix const* obpf_tetrion_matrix(struct ObpfTetrion const* tetrion);
     OBPF_EXPORT uint8_t obpf_tetrion_width(void);
     OBPF_EXPORT uint8_t obpf_tetrion_height(void);
+    OBPF_EXPORT uint8_t obpf_tetrion_num_invisible_lines(void);
 
     // Matrix
-    OBPF_EXPORT ObpfTetrominoType obpf_matrix_get(struct ObpfMatrix const* matrix, ObpfVec2 position);
+    OBPF_EXPORT ObpfTetrominoType obpf_tetrion_matrix_get(const struct ObpfTetrion* tetrion, ObpfVec2 position);
 
     // clang-format on
 
diff --git a/src/obpf/simulator.cpp b/src/obpf/simulator.cpp
index 794c208..731c5ff 100644
--- a/src/obpf/simulator.cpp
+++ b/src/obpf/simulator.cpp
@@ -48,10 +48,12 @@ ObpfLineClearDelayState obpf_tetrion_get_line_clear_delay_state(ObpfTetrion cons
     }
     return ObpfLineClearDelayState{
         .count = gsl::narrow<u8>(original_size),
-        .first = lines.at(0),
-        .second = lines.at(1),
-        .third = lines.at(2),
-        .fourth = lines.at(3),
+        .lines{
+               lines.at(0),
+               lines.at(1),
+               lines.at(2),
+               lines.at(3),
+               },
         .countdown = countdown,
         .delay = LineClearDelay::delay,
     };
@@ -77,15 +79,6 @@ void obpf_destroy_tetrion(ObpfTetrion const* const tetrion) {
     delete tetrion;
 }
 
-ObpfMatrix const* obpf_tetrion_matrix(ObpfTetrion const* const tetrion) {
-    return reinterpret_cast<ObpfMatrix const*>(std::addressof(tetrion->matrix()));
-}
-
-ObpfTetrominoType obpf_matrix_get(ObpfMatrix const* const matrix, ObpfVec2 const position) {
-    auto const pos = Vec2{ position.x, position.y };
-    return static_cast<ObpfTetrominoType>((*reinterpret_cast<Matrix const*>(matrix))[pos]);
-}
-
 uint8_t obpf_tetrion_width() {
     return uint8_t{ Matrix::width };
 }
@@ -94,6 +87,15 @@ uint8_t obpf_tetrion_height() {
     return uint8_t{ Matrix::height };
 }
 
+uint8_t obpf_tetrion_num_invisible_lines() {
+    return uint8_t{ Matrix::num_invisible_lines };
+}
+
+ObpfTetrominoType obpf_tetrion_matrix_get(ObpfTetrion const* const tetrion, ObpfVec2 const position) {
+    auto const pos = Vec2{ position.x, position.y };
+    return static_cast<ObpfTetrominoType>(tetrion->matrix()[pos]);
+}
+
 ObpfPreviewPieces obpf_tetrion_get_preview_pieces(ObpfTetrion const* tetrion) {
     auto const preview_tetrominos = tetrion->get_preview_tetrominos();
     ObpfPreviewPieces result{};
diff --git a/src/simulator/include/simulator/matrix.hpp b/src/simulator/include/simulator/matrix.hpp
index 2ff6817..626b029 100644
--- a/src/simulator/include/simulator/matrix.hpp
+++ b/src/simulator/include/simulator/matrix.hpp
@@ -10,6 +10,7 @@ class Matrix final {
 public:
     static constexpr auto width = std::size_t{ 10 };
     static constexpr auto height = std::size_t{ 22 };
+    static constexpr auto num_invisible_lines = std::size_t{ 2 };
 
 private:
     std::array<TetrominoType, width * height> m_minos{};
diff --git a/src/simulator/include/simulator/tetrion.hpp b/src/simulator/include/simulator/tetrion.hpp
index 45da692..6192c1b 100644
--- a/src/simulator/include/simulator/tetrion.hpp
+++ b/src/simulator/include/simulator/tetrion.hpp
@@ -83,6 +83,7 @@ struct ObpfTetrion final {
 
 private:
     void freeze_and_destroy_active_tetromino();
+    [[nodiscard]] bool is_tetromino_completely_visible(Tetromino const& tetromino) const;
     [[nodiscard]] bool is_tetromino_position_valid(Tetromino const& tetromino) const;
     [[nodiscard]] bool is_active_tetromino_position_valid() const;
     void spawn_next_tetromino();
diff --git a/src/simulator/tetrion.cpp b/src/simulator/tetrion.cpp
index 75a93f1..582b351 100644
--- a/src/simulator/tetrion.cpp
+++ b/src/simulator/tetrion.cpp
@@ -131,6 +131,20 @@ void ObpfTetrion::freeze_and_destroy_active_tetromino() {
     m_active_tetromino = std::nullopt;
 }
 
+[[nodiscard]] bool ObpfTetrion::is_tetromino_completely_visible(Tetromino const& tetromino) const {
+    if (not is_tetromino_position_valid(tetromino)) {
+        return false;
+    }
+
+    for (auto const& position : get_mino_positions(tetromino)) {
+        if (position.y < gsl::narrow<i32>(Matrix::num_invisible_lines)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 [[nodiscard]] bool ObpfTetrion::is_tetromino_position_valid(Tetromino const& tetromino) const {
     auto const mino_positions = get_mino_positions(tetromino);
     for (auto const position : mino_positions) {
@@ -170,6 +184,21 @@ void ObpfTetrion::spawn_next_tetromino() {
         m_is_hold_possible = true;
     }
 
+    // todo: check game over state here
+
+    // clang-format off
+    for (
+        auto i = std::size_t{ 0 };
+        not is_tetromino_completely_visible(active_tetromino().value()) and i < Matrix::num_invisible_lines;
+        ++i
+    ) {  // clang-format on
+        m_active_tetromino->position.y += 1;
+        if (not is_active_tetromino_position_valid()) {
+            m_active_tetromino->position.y -= 1;
+            break;
+        }
+    }
+
     m_is_soft_dropping = false;
     m_next_gravity_frame = m_next_frame + gravity_delay_by_level(level());
 }