Hey Kaisuo, This was posted on BlitzCoder.com by Nebula. Its a wonderfully commented, simple to understand tutorial on how to make a basic basic platformer. Its invaluable to noobs.
Open in online IDE; (Coded by Nebula) ; (date : 02-2001)(update : 04-2001) ; (Commented in 12-2003) ; Visit <A HREF="http://www.geocities.com\nebula_rve" TARGET=_blank>www.geocities.com\nebula_rve</A> for more examples ; Visit <A HREF="http://hardcorecoder.com" TARGET=_blank>http://hardcorecoder.com</A> for DaCodez ; ; Function Introduction() ; ; Small Platform Example - Re-documented in 2003 ; ; ; ; ; End Function Graphics 640,480 SetBuffer BackBuffer() ; ; Load 2 images. One being the 'dude' that will be controlled by the player. The other 'tile' ; will be used to draw the game playing field. ; Global dude = CreateImage(32,32);LoadImage("dude.bmp") Global tile = CreateImage(32,32);LoadImage("tile.bmp") ; SetBuffer ImageBuffer(dude) ClsColor 255,255,255 Cls SetBuffer ImageBuffer(tile) ClsColor 100,100,100 Cls SetBuffer BackBuffer() ClsColor 0,0,0 ; ; Create two arrays that are required to display the map. The 'map' array will hold each tile that is drawn/displayed ; on the screen. ;The map1$ array hold the level information. This array is a string because the levels are stored inside this ; sourcecode as text. Using text means more then 10 characters can be used to build the screen. Dim map(19,14) Dim map1$(14) ; ; Here the regular global game values are set up. Being global means these variables can be accesed from ; anywhere inside the program. ; dudex = holds the character x position. The x position is the most left position of the sprite/image. ; dude7 = holds the character y position. This means the most top position of the sprite. ; Jump = holds TRue when the player jumped and holds false when not or when landed. ; jumptimer# = a float value that is used to time/adjust the speed at which the jumping and ; falling happens. ; Global dudex Global dudey Global jump Global jumptimer# ; Start location - The player will begin at this position when the game starts. dudex = 200 dudey = 320 ; ; Here the level is set up. Each array string hold a number of lines. ; With the 1 value we will tell the program that there is a wall/floor there ; and with 0 we tell that there is nothing there that should be drawn. ; map1$(0) = "1111111111111111111" map1$(1) = "1000000000000000001" map1$(2) = "1000000000000000001" map1$(3) = "1000001111111111001" map1$(4) = "1000000000000000001" map1$(5) = "1111110000000000001" map1$(6) = "1000000000000000001" map1$(7) = "1111111100000000001" map1$(8) = "1000000000000000001" map1$(9) = "1000000011111111111" map1$(10) = "1000000000000000001" map1$(11) = "1111111000000000001" map1$(12) = "1000000000000000001" map1$(13) = "1000000001111111111" map1$(14) = "1111111111111111111" ; ; Using strings inside game loops for quickly reading information is not the fastest method. ; By converting these values into integers they will become much faster. ; Blitz automatically converts string integers into integers. Using other strings than numbers ; requires special code. ; ; ; For y=0 To 14 ; 14 = the number of vertical tiles that can fit in the screenmode. The map array is based on this. For x=0 To 19 ; 19 is the number of horizontal tiles that can fit in the screenmode. n = Mid(map1$(y),x+1,1) map(x,y)=Int(n) Next Next ; ; This is the game loop. It exits when the escape key is pressed (keydown(1) = true) ; While KeyDown(1) = False Cls drawmap() ; draw the graphics movedude(); read the players movement checkjump() ; update the code that controls the jump drawsprite() ; draw the player Flip Wend End Function movedude() ; ; This function contains all code to move the player inside the game level. ; ; ; ; Keydown 203 tells the left cursor key is pressed. When it is pressed a local variable is initiated that will tell ; the code below that the key is pressed. Same goes with the 205 keycode which is the right cursor key. ; If KeyDown(203)=True Then moveleft=True If KeyDown(205)=True Then moveright=True ; border checking ; ; The width of a tile in this example is 32 pixels. This means our player which x position is the most left ; position of the player graphic would touch a wall when he is on the screen position of 32. Going below ; this position would mean he is inside a wall. This is why we will not allow him to go below 32. ; By resetting the previously set value we ensure he will not go thru a wall. ; ; The right side position of the screen is the number of tiles that can fit in the graphicsmode. Seeing this ; can be calculated by dividing the screenwidth and the tilewidth we know it is 20 tiles. Blitz however ; also uses Zero as a number so this means we should substract 1 from the actual number a calculator would give. ; When knowing the player width is also 32 and his draw coordinates are from the most left this means we should ; substract another 1 to get the correct position. This example leaves one 32 pixel space open to the right which ; means another substraction. This space could be used for game info ect. ; 17*32 will return the location of the outer wall of this map. ; If dudex<32 Then moveleft=False If dudex>(17*32) Then moveright=False ; movement x with or without jumping ; ; In this example we can jump thru platforms above the player. This is done by checking for collisions when ; the player is NOT jumping. This way he can move to the left and right and thru objects while going up. ; When he is not jumping the collision is checked and will the land on the first tile below him. ; The actual falling back on a tile is done in the jump function. ; The collision works by checking the array using the player coordinates. By dividing these with the ; width and height of a tile the array position gets returned. The array holds 1 for a tile. So by ; checking this value and not seing it we allow the player to move around. ; ; No gravity means checking collision. And Gravity means freedom in horizontal movement. ; ; If jump=False Then If Not map(dudex/32,dudey/32)=1 Then If moveleft=True Then dudex=dudex-4 End If If Not map((dudex+32)/32,dudey/32) = 1 Then If moveright=True Then dudex=dudex+4 End If Else If moveleft=True Then dudex=dudex-3 If moveright=True Then dudex=dudex+3 EndIf End Function Function checkjump() ; The keydown 57 signals the space key is being pressed. When this happens ; the code then checks to see if no jump is actually in progress. If it is and it is not ; check then the player would keep moving up until he is out of the screen and this ; will cause the compiler to return a error(array out of bounds). ; When the player is not jumping the jump variable is set to TRUE and the jumptimer(or height) ; is set to its value. ; If KeyDown(57)=True If jump=False jump=True jumptimer=8 End If End If ; ; While the character is in a jump a number of things should happen. Gravity has the effect ; that once you take off the ground the speed at which you travel decreases until it becomes ; negative(falling down). This happens slowly but incremental (ea speed+1 until 0 and speed-1 until ground) ; The code below uses a float value. Floats are integers divided into integers. The amount of integers in a float ; can be very high or low just like regular numbers. The jumptimer with which the jump is measured uses ; a value of .33. Which is 1/3 of the number 1. ; Above the jumpforce is set to 8. The speed starts at 8 pixels going up every cycle and decreases by ; .33 every cycle until it becomes negative and means the player wil start to move down. This also happens ; with .33 per cycle and thus emulates gravity. ea The player will stop for a while in the air and slowly start ; to fall down; ; Once a tile below the player is found (player coordinates divided by the tileheight and one extra to compensate ; for the height of the player) the gravity is disabled. ; Because the player is falling down using large chunks he would end up inside a tile. This is why once a collision ; happens the coordinates are 'RESET'' to the tile that it collides with. This will ensure no errors happen. ; Do remember that once the speed of the falling gets above the tileheight he will fall thru no matter what. This ; can be avoided by limiting the falling speed to a maximum. Like 8 for instance. ; ; ; Here we go up ; ; ; If we are in the progress of a jump If jump=True Then ; decrease the jumptimer jumptimer=jumptimer-0.33 ; move the y axis of the dude dudey=dudey-jumptimer ; if the jumptimer is below zero If jumptimer=<0 Then ; If we are on a floor If map((dudex+16)/32,(dudey+32)/32) = 1 Then ; stopp falling jump=False ; Align the player with the floor tempy = dudey/32 dudey = tempy*32 End If End If End If ; ; To ensure the player fall down from platforms a extra piece of code is required. By checking collision ; with tiles every cycle and setting the jump value to true when no collision is happening the player will ; start to fall. The falling can be done by puttin the jumptimer to ZERO. This means in stead of going up ; when it is 8 he wil go up by ZERO And Then decrease down Until a collision happens(Floor). ; ; The jump flag is false so the player is on a tile. ; If No collision ; Fall down. ; If jump=False Then If Not map((dudex+16)/32,(dudey+32)/32) = 1 Then jump=True : jumptimer=0 End If End If ; don't allow the dude To get stuck in the ceiling ; ; The top of the player is the y coordinate of the player. This because of the way blitz draws its ; default sprites. By checking if the player y coordinate is less then zero it can be seen when ; the player is about to leave the visible screen. By resetting this value to in this case 5 he will never ; be able to leave the screen. The jump variable will also be SET to ensure the player will start to fall ; down. This again by setting the fallingtimer(or gravity) to ZERO. ; If dudey < 0 Then dudey = 5 jump=True : jumptimer=0 EndIf End Function Function drawsprite() ; ; The regular draw command. ; DrawImage dude,dudex,dudey End Function Function drawmap() ; ; This routine draw the entire visible playing map. The width and height ; of the graphicsscreen are known and the width and height of the tiles are. ; Then by using a nested loop and checking when the map array contains a tile (1) ; the program draws it. The location of the tile can be calculated by taking the ; width or height and multiplying it with the nested loop value. ; ; For y=0 To 14 For x=0 To 19 If map(x,y)=1 Then DrawImage tile,x*32,y*32 End If Next Next End Function