/*
    Rabih Kaddour
    http://kaddour-es.de/
    August, 2016.
*/

.correct_image, .wrong_image {
    position: relative;
    width:128px;
    height: 128px;
    visibility: hidden;
    background-size:contain; /* fit image */
}

.correct_image {
	background: url("../img/answerOk.png") no-repeat;
}

.wrong_image {
	background: url(../img/answerError.png) no-repeat;
}

.img-checkmark {
    display:block;
    min-height: 16px;
    min-width: 16px;
    /*background: url(../img/check_mark.png) no-repeat;*/
    background: url(../img/tick_16.png) no-repeat;
    background-size:contain; /* fit image */
    background-color:none;
    /*center*/
    margin-left:auto;
    margin-right:auto;
    margin-top:72px;
    visibility:hidden;
}

/********************************************* parabola  *************************************************************************************/
.img_parabola_ref {
    background: url(../img/parabola/parabola-names_ref.svg) no-repeat;
}
.img_parabola_1 {
    background: url(../img/parabola/img_parabola_1.svg) no-repeat;
}
.img_parabola_1_ans {
    background: url(../img/parabola/img_parabola_1_ans.svg) no-repeat;
}
.img_parabola_2 {
    background: url(../img/parabola/img_parabola_2.svg) no-repeat;
}
.img_parabola_2_ans {
    background: url(../img/parabola/img_parabola_2_ans.svg) no-repeat;
}
.img_parabola_3 {
    background: url(../img/parabola/img_parabola_3.svg) no-repeat;
}
.img_parabola_3_ans {
    background: url(../img/parabola/img_parabola_3_ans.svg) no-repeat;
}
.img_parabola_4 {
    background: url(../img/parabola/img_parabola_4.svg) no-repeat;
}
.img_parabola_4_ans {
    background: url(../img/parabola/img_parabola_4_ans.svg) no-repeat;
}

.img_parabola_ref,
.img_parabola_1, .img_parabola_1_ans,
.img_parabola_2, .img_parabola_2_ans,
.img_parabola_3, .img_parabola_3_ans,
.img_parabola_4, .img_parabola_4_ans {
  display: block;
  min-height: 250;
  min-width: 250;
  background-size:contain;
  visibility:visible;
}

/********************************************* angle  *************************************************************************************/
.img_quad_16_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_16_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_16_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_16_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_62_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_62_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_62_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_62_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_61_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_61_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_61_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_61_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_87_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_87_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_87_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_87_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_145_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_145_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_quad_145_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/quad_145_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_60_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_60_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_60_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_60_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_17_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_17_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_17_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_17_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_32_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_32_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_32_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_32_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_26_angle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_26_angle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_tri_26_angle_answer {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/angle/tri_26_angle_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
/********************************************* classify triangles *************************************************************************/
/********************************************* explain *********/
.img_equilateral_triangle_def {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/equilateral_triangle_def.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_isosceles_triangle_def {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/isosceles_triangle_def.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_scalene_triangle_def {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/scalene_triangle_def.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_acute_triangle_def {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/acute_triangle_def.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_right_triangle_def {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/right_triangle_def.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_obtuse_triangle_def {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/obtuse_triangle_def.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
/********************************************* end explain *********/
.img_right_isosceles_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/right_isosceles_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_right_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/right_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_right_triangle2 {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/right_triangle2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_obtuse_isosceles_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/obtuse_isosceles_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_scalene_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/scalene_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_isosceles_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/isosceles_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_isosceles_triangle2 {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/isosceles_triangle2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_isosceles_triangle3 {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/isosceles_triangle3.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_equilateral_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/equilateral_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_acute_triangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/classify/acute_triangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
/********************************************* quadrilaterals *****************************************************************************/
.img_quadrilateral_rectangle {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/quadrilaterals/quadrilateral_rectangle.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_quadrilateral_square {
    display:inline-block;
    min-height: 188px;
    min-width: 188px;
    background: url(../img/quadrilaterals/quadrilateral_square.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_quadrilateral_rhombus {
    display:inline-block;
    min-height: 188px;
    min-width: 188px;
    background: url(../img/quadrilaterals/quadrilateral_rhombus.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_quadrilateral_parallelogram {
    display:inline-block;
    min-height: 256px;
    min-width: 256px;
    background: url(../img/quadrilaterals/quadrilateral_parallelogram.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_quadrilateral_trapezium {
    display:inline-block;
    min-height: 305px;
    min-width: 164px;
    background: url(../img/quadrilaterals/quadrilateral_trapezium.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

/********************************************* perpendicular, parallel and intersection ************************************************************************/
.img-line-perp-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_not_perpendicular1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-perp-1-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_not_perpendicular1_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-1-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel1_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel2_2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-2-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel2_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-3 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel3.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-3-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel3_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-4 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel4.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-para-4-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_parallel4_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-perpend-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_perpendicular1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-perpend-1-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_perpendicular1_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-inters-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_intersecting1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-line-inters-1-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/line-plane/line_intersecting1_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

/********************************************* count vertices, edges, faces ***********************************************************************************/

.img-cube-vertices {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube_vertices.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube-vertices-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube_vertices_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube2-vertices {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube2_vertices.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube2-vertices-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube2_vertices_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube-faces {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube_faces.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube-faces-tb-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube_answer_step1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube-faces-lr-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube_answer_step4.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube-faces-fb-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube_answer_step3.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube2-faces {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube2_faces.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube2-faces-step1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube2_answer_step1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cube2-faces-step2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cube2_answer_step2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-prism-vertices {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/prism_vertices.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-prism-vertices-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/prism_vertices_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-prism-faces {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/prism_faces.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-prism-faces-step1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/prism_answer_step1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-prism-faces-step2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/prism_answer_step2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cylinder-faces {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cylinder_faces.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cylinder-faces-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cylinder_faces_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cylinder-faces-2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cylinder_faces_answer_2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cylinder-edges-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cylinder_edges_1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cylinder-edges-2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cylinder_edges_2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}


.img-cone-edges {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cone.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cone-edges-1 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cone_edges_1.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cone-edges-2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/count/cone_edges_2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

/********************************************* area **********************************************************************************************************/
.img-cell10-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_10.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell10-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_10_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell10-a-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_10_a.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell10-a-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_10_a_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell13-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_13.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell13-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_13_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell14-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_14.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell14-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_14_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell14_blue-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_14_blue.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell14_blue-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_14_blue_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell15-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_15.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell15-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_15_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell20-area {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_20.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cell20-area_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/area/cell_20_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

/********************************************* coordinates **************************************************************************************************/
.img_point_24_minus {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    /*background: url(../img/coordinates/cartesian_coordinates.svg) no-repeat;*/
    background: url(../img/coordinates/coord_minus_24.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}
.img_point_24_minus_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_minus_24_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_32_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_32_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_52_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_minus_52.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_22_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_minus_22_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_2 {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_2.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_55_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_minus_55_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_42_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_minus_42_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_33_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_minus_33_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img_point_34_answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/coordinates/coord_34_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

/********************************************* perimeter ****************************************************************************************************/

.img-hexagon-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/hexagon_30.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-star-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/star_24.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-rect-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/rectangle_38.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-pentagon-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/pentagon_25.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-pentagon-peri-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/pentagon_25_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-cross-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/kreuz_34.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-boat-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/boat_36.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-l-unit-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/l_unit_14.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-l-unit-peri-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/l_unit_14_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-u-unit-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/u_unit_22.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-u-unit-peri-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/u_unit_22_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-t-unit-peri {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/t_unit_12.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

.img-t-unit-peri-answer {
    display:inline-block;
    min-height: 128px;
    min-width: 128px;
    background: url(../img/perimeter/t_unit_12_answer.png) no-repeat;
    background-size:contain;
    vertical-align:middle;
    visibility:visible;
    display:normal;
}

/********************************************* Three-dimensional forms ***************************************************************************************/

.img-cone2 {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/coneA256.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-cusp {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/cusp_hat_cone.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-bucket {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/basket_trash.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-ring {
    display:block;
    min-height: 175px;
    min-width: 175px;
    /*background: url(../img/engagement-ring.png) no-repeat;*/
    background: url(../img/ring-128.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-earth2 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/earth.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-pyramid2 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/pyramid_egypt.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-camping {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/camping_prism.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cube2 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/milk-package_cube.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-fireplace {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/fireplace.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cylinder-bucket {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/cylinder_bucket.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-basktball {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/basketball_sphere.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-football {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/football.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

/********************************************* Three-dimensional shapes ***************************************************************************************/

.img-cube {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/cube.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cube1 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cube1.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cone-form {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cone-wood.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-cone {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/cone256.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-cone-1 {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cone1.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-cone-2 {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cone2.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-sphere-form {
    display: block;
    min-height: 175px;
    min-width: 175px;
    /*background: url(../img/sphere256.png) no-repeat;*/
    background:url(../img/shape/sphere-jade.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-sphere {
    display: block;
    min-height: 175px;
    min-width: 175px;
    /*background: url(../img/sphere256.png) no-repeat;*/
    background:url(../img/sphere_ball.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-sphere1 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    /*background: url(../img/sphere256.png) no-repeat;*/
    background:url(../img/shape/sphere1.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-sphere2 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    /*background: url(../img/sphere256.png) no-repeat;*/
    background:url(../img/shape/sphere2.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cylinder-form {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cylinder-wood.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cylinder {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/cylinder256.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cylinder1 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cylinder_1.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-cylinder2 {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/cylinder_2.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-pyramid {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/pyramid256.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

.img-torus {
    display: block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/torus256.png) no-repeat;
    background-size: contain;
    visibility: visible;
}

/********************************************* Two-dimensional shapes ***************************************************************************************/
.img-star {
    display:block; /* for verification */
    min-height: 125px; /* for verification */
    min-width: 125px; /* for verification */
    background: url(../img/star-128.png) no-repeat;
    background-size:contain; /* fit image */
}

.img-stara {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/stara.png) no-repeat;
    background-size:contain;
}

.img-star-form {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/sea-star.jpg) no-repeat;
    background-size:contain;
}

.img-star-form-2 {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/sea-star2.png) no-repeat;
    background-size:contain;
}

.img-rhombus {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/rhombus.png) no-repeat;
    background-size:contain;
    margin-left:auto;
    margin-right:auto;
}

.img-rhombus-form {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/rhombus-form.png) no-repeat;
    background-size:contain;
}

.img-rhombus-form-2 {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/rhombus-form-2.png) no-repeat;
    background-size:contain;
}

.img-triangle {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/triangle.png) no-repeat;
    background-size:contain;
}

.img-trianglea {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/trianglea.png) no-repeat;
    background-size:contain;
}

.img-rectangle {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/rectangle.png) no-repeat;
    background-size:contain;
}

.img-rect-form {
    display:block;
    min-height: 175px;
    min-width: 175px;
    background: url(../img/shape/rectForm.png) no-repeat;
    background-size:contain;
    visibility:visible;
}

.img-rectanglea {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/rectanglea.png) no-repeat;
    background-size:contain;
}

.img-square {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/square.png) no-repeat;
    background-size:contain;
}

.img-square-form {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/solid-square-table-top.png) no-repeat;
    background-size:contain;
}

.img-hexagon {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/hexagon.png) no-repeat;
    background-size:contain;
}

.img-hexagon-form {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/hexagonForm1.png) no-repeat;
    background-size:contain;
}

.img-hexagon-form-2 {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/hexagonForm2.png) no-repeat;
    background-size:contain;
}

.img-circle {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/circle.png) no-repeat;
    background-size:contain;
}

.img-circle-form {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/shape/circ_form.png) no-repeat;
    background-size:contain;
}

.img-circle-form-2 {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/shape/circ_form-2.jpg) no-repeat;
    background-size:contain;
}

.img-circlea {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/circle_128.png) no-repeat;
    /*background: url(../img/circlefill.png) no-repeat;*/
    background-size:contain;
    /*center*/
    margin-left:auto;
    margin-right:auto;
}

.img-trapeze {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/trapeze.png) no-repeat;
    background-size:contain;
    /*center*/
    margin-left:auto;
    margin-right:auto;
}

.img-pentagon {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/pentagon.png) no-repeat;
    background-size:contain;
    /*center*/
    margin-left:auto;
    margin-right:auto;
}

.img-pentagon-form {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/shape_pentagon-form.png) no-repeat;
    background-size:contain;
}

.img-pentagon-form-2 {
    display:block;
    min-height: 100px;
    min-width: 100px;
    background: url(../img/shape/pentagonForm2.png) no-repeat;
    background-size:contain;
}

.img-line {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/shape_line.png) no-repeat;
    background-size:contain;
}

.img-elipse {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/ellipse.png) no-repeat;
    background-size:contain;
}

.img-oval {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/oval.png) no-repeat;
    background-size:contain;
}

.img-diamond {
    display:block;
    min-height: 125px;
    min-width: 125px;
    background: url(../img/diamond.png) no-repeat;
    background-size:contain;
}

.img-arrow-up {
    display:inline-block;
    min-height: 43px;
    min-width: 43px;
    background: url(../img/arrow_up.png) no-repeat;
    background-size:contain;
}

.img-delete {
    display:inline-block;
    min-height: 40px;
    min-width: 40px;
    background: url(../img/delete.png) no-repeat;
    background-size:contain;
}

.img-done {
    display:block; /* for verification */
    min-height: 140px; /* for verification */
    min-width: 140px; /* for verification */
    background: url(../img/task_completed.png) no-repeat;
    background-size:contain; /* fit image */
}